Core/Spells: Added very little tolerance level to completed casts to ensure that spell cast at target standing at the max possible range is finished properly even if target moves a little (#18969)

(cherry-picked from 66dc97bb27)

src/server/game/Spells/Spell.cpp

@@ -2892,6 +2892,9 @@ bool Spell::UpdateChanneledTargetList()
         range = m_spellInfo->GetMaxRange(m_spellInfo->IsPositive());
         if (Player* modOwner = m_caster->GetSpellModOwner())
             modOwner->ApplySpellMod(m_spellInfo->Id, SPELLMOD_RANGE, range, this);
+
+        // add little tolerance level
+        range += std::min(MAX_SPELL_RANGE_TOLERANCE, range*0.1f); // 10% but no more than MAX_SPELL_RANGE_TOLERANCE
     }
 
     for (std::vector<TargetInfo>::iterator ihit = m_UniqueTargetInfo.begin(); ihit != m_UniqueTargetInfo.end(); ++ihit)
@@ -6125,6 +6128,10 @@ SpellCastResult Spell::CheckRange(bool strict) const
     float minRange, maxRange;
     std::tie(minRange, maxRange) = GetMinMaxRange(strict);
 
+    // dont check max_range to strictly after cast
+    if (m_spellInfo->RangeEntry && m_spellInfo->RangeEntry->Flags != SPELL_RANGE_MELEE && !strict)
+        maxRange += std::min(MAX_SPELL_RANGE_TOLERANCE, maxRange*0.1f); // 10% but no more than MAX_SPELL_RANGE_TOLERANCE
+
     // get square values for sqr distance checks
     minRange *= minRange;
     maxRange *= maxRange;

src/server/game/Spells/Spell.h

@@ -65,6 +65,7 @@ enum TriggerCastFlags : uint32;
 enum WeaponAttackType : uint8;
 
 #define SPELL_CHANNEL_UPDATE_INTERVAL (1 * IN_MILLISECONDS)
+#define MAX_SPELL_RANGE_TOLERANCE 3.0f
 
 enum SpellCastFlags
 {