Core/Creatures: Stop falling if corpse is removed (can happen when alive unit is despawned instantly in air) (#18995)

Do not allow to start waypoint movement when unit is dead

(cherry-picked from f86ca9e3c9)

src/server/game/Entities/Creature/Creature.cpp

@@ -287,6 +287,10 @@ void Creature::RemoveCorpse(bool setSpawnTime)
     if (setSpawnTime)
         m_respawnTime = time(NULL) + respawnDelay;
 
+    // if corpse was removed during falling, the falling will continue and override relocation to respawn position
+    if (IsFalling())
+        StopMoving();
+
     float x, y, z, o;
     GetRespawnPosition(x, y, z, &o);
     SetHomePosition(x, y, z, o);

src/server/game/Movement/MovementGenerators/WaypointMovementGenerator.cpp

@@ -120,6 +120,9 @@ bool WaypointMovementGenerator<Creature>::StartMove(Creature* creature)
     if (!i_path || i_path->nodes.empty())
         return false;
 
+    if (Stopped())
+        return true;
+
     bool transportPath = creature->GetTransport() != nullptr;
 
     if (IsArrivalDone)