Fix some compiler warnings reported by GCC (#25007)

* Core/AI: Remove unneeded null checks

GetMap() can never return NULL.

Fixes additionally -Wunused-variable warnings
reported by GCC.

* Core/GameObject: Fix a -Wunused-variable warning reported by GCC

* Core/Player: Fix a -Wunused-variable warning reported by GCC

* Scritps/CavernsOfTime: Fix -Wimplicit-fallthrough warnings reported by GCC

* Scritps/CavernsOfTime: Fix a -Wmaybe-uninitialized warning reported by GCC

Warning:

/home/peterke/DEV/TrinityCore/src/server/scripts/Kalimdor/CavernsOfTime/CullingOfStratholme/npc_arthas.cpp: In member function ‘virtual void npc_arthas_stratholme::npc_arthas_stratholmeAI::UpdateAI(uint32)’:
/home/peterke/DEV/TrinityCore/src/server/scripts/Kalimdor/CavernsOfTime/CullingOfStratholme/npc_arthas.cpp:1119:58: warning: ‘emote’ may be used uninitialized in this function [-Wmaybe-uninitialized]
 1119 |                                 (*it)->HandleEmoteCommand(emote);
      |                                 ~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~

* Scritps/PitOfSaron: Fix -Wunused-variable warnings reported by GCC

* Scritps/EyeOfEternity: Fix a -Wclass-memaccess warning reported by GCC

Warning:

/home/peterke/DEV/TrinityCore/src/server/scripts/Northrend/Nexus/EyeOfEternity/boss_malygos.cpp: In member function ‘virtual void boss_malygos::boss_malygosAI::UpdateAI(uint32)’:
/home/peterke/DEV/TrinityCore/src/server/scripts/Northrend/Nexus/EyeOfEternity/boss_malygos.cpp:950:81: warning: ‘void* memset(void*, int, size_t)’ clearing an object of non-trivial type ‘class ObjectGuid’; use assignment or value-initialization instead [-Wclass-memaccess]
  950 |                             memset(_surgeTargetGUID, 0, sizeof(_surgeTargetGUID));
      |

* Scritps/CoilfangReservoir: Fix a -Wclass-memaccess warning reported by GCC

Warning:

/home/peterke/DEV/TrinityCore/src/server/scripts/Outland/CoilfangReservoir/SerpentShrine/boss_leotheras_the_blind.cpp: In member function ‘void boss_leotheras_the_blind::boss_leotheras_the_blindAI::Initialize()’:
/home/peterke/DEV/TrinityCore/src/server/scripts/Outland/CoilfangReservoir/SerpentShrine/boss_leotheras_the_blind.cpp:220:55: warning: ‘void* memset(void*, int, size_t)’ clearing an object of non-trivial type ‘class ObjectGuid’; use assignment or value-initialization instead [-Wclass-memaccess]
  220 |             memset(InnderDemon, 0, sizeof(InnderDemon));
      |                                                       ^

* Scritps/Naxx: Fix a -Wimplicit-fallthrough warning reported by GCC

For discussion see https://github.com/TrinityCore/TrinityCore/pull/25007

(cherry picked from commit 10be49bdfe)

src/server/scripts/EasternKingdoms/BlackrockMountain/BlackrockSpire/instance_blackrock_spire.cpp

@@ -298,6 +298,7 @@ public:
                         if (GetBossState(DATA_DRAGONSPIRE_ROOM) != DONE)
                             Events.ScheduleEvent(EVENT_DARGONSPIRE_ROOM_STORE, 1s);
                     }
+                    break;
                 case DATA_BLACKHAND_INCARCERATOR:
                     for (GuidList::const_iterator itr = _incarceratorList.begin(); itr != _incarceratorList.end(); ++itr)
                         if (Creature* creature = instance->GetCreature(*itr))

src/server/scripts/Kalimdor/CavernsOfTime/CullingOfStratholme/boss_salramm_the_fleshcrafter.cpp

@@ -110,7 +110,7 @@ class boss_salramm : public CreatureScript
                         break;
                     case EVENT_EXPLODE_GHOUL2:
                         events.ScheduleEvent(EVENT_SUMMON_GHOULS, Seconds(4));
-                        // intentional missing break
+                        /* fallthrough */
                     case EVENT_EXPLODE_GHOUL1:
                         Talk(SAY_EXPLODE_GHOUL);
                         DoCastAOE(SPELL_EXPLODE_GHOUL, true);

src/server/scripts/Kalimdor/CavernsOfTime/CullingOfStratholme/culling_of_stratholme.cpp

@@ -361,7 +361,7 @@ class npc_chromie_start : public CreatureScript
                         break;
                     case GOSSIP_OFFSET_SKIP_1:
                         AdvanceDungeonFar();
-                        // intentional missing break
+                        /* fallthrough */
                     case GOSSIP_OFFSET_TELEPORT:
                         CloseGossipMenuFor(player);
                         me->CastSpell(player, SPELL_TELEPORT_PLAYER);

src/server/scripts/Kalimdor/CavernsOfTime/CullingOfStratholme/npc_arthas.cpp

@@ -1095,28 +1095,17 @@ public:
                         me->GetCreatureListWithEntryInGrid(nearbyVictims, urand(0, 1) ? NPC_CITIZEN : NPC_RESIDENT, 60.0f);
                         if (!nearbyVictims.empty())
                         {
-                            std::list<Creature*>::iterator it = nearbyVictims.begin();
-                            std::advance(it, urand(0, nearbyVictims.size()-1));
-                            Emote emote;
-                            switch (urand(0, 3))
+                            Emote emotes[] =
                             {
-                                case 0:
-                                    emote = EMOTE_ONESHOT_TALK;
-                                    break;
-                                case 1:
-                                    emote = EMOTE_ONESHOT_EXCLAMATION;
-                                    break;
-                                case 2:
-                                    emote = EMOTE_ONESHOT_RUDE;
-                                    break;
-                                case 3:
-                                    emote = EMOTE_ONESHOT_ROAR;
-                                    break;
-                                default:
-                                    break;
-                            }
-                            if ((*it)->IsAlive())
-                                (*it)->HandleEmoteCommand(emote);
+                                EMOTE_ONESHOT_TALK,
+                                EMOTE_ONESHOT_EXCLAMATION,
+                                EMOTE_ONESHOT_RUDE,
+                                EMOTE_ONESHOT_ROAR
+                            };
+
+                            Creature* victim = Trinity::Containers::SelectRandomContainerElement(nearbyVictims);
+                            if (victim->IsAlive())
+                                victim->HandleEmoteCommand(Trinity::Containers::SelectRandomContainerElement(emotes));
                         }
                         break;
                     }

src/server/scripts/Northrend/FrozenHalls/PitOfSaron/instance_pit_of_saron.cpp

@@ -157,7 +157,7 @@ class instance_pit_of_saron : public InstanceMapScript
                     case DATA_GARFROST:
                         if (state == DONE)
                         {
-                            if (Creature* summoner = instance->GetCreature(_garfrostGUID))
+                            if (instance->GetCreature(_garfrostGUID))
                             {
                                 if (_teamInInstance == ALLIANCE)
                                 {
@@ -175,7 +175,7 @@ class instance_pit_of_saron : public InstanceMapScript
                     case DATA_TYRANNUS:
                         if (state == DONE)
                         {
-                            if (Creature* summoner = instance->GetCreature(_tyrannusGUID))
+                            if (instance->GetCreature(_tyrannusGUID))
                             {
                                 if (_teamInInstance == ALLIANCE)
                                 {

src/server/scripts/Northrend/Naxxramas/boss_thaddius.cpp

@@ -402,6 +402,7 @@ struct boss_thaddius : public BossAI
                         break;
                     case EVENT_ENABLE_BALL_LIGHTNING:
                         ballLightningUnlocked = true;
+                        break;
                     case EVENT_ENGAGE:
                         me->SetReactState(REACT_AGGRESSIVE);
                         break;