Core/Unit: don't use damage immunity to calculate hit result for the whole spell. Should be used only for damage

src/server/game/Entities/Unit/Unit.cpp

@@ -666,6 +666,12 @@ void Unit::DealDamageMods(Unit const* victim, uint32 &damage, uint32* absorb) co
 
 uint32 Unit::DealDamage(Unit* victim, uint32 damage, CleanDamage const* cleanDamage, DamageEffectType damagetype, SpellSchoolMask damageSchoolMask, SpellInfo const* spellProto, bool durabilityLoss)
 {
+    if (victim->IsImmunedToDamage(spellProto))
+    {
+        SendSpellDamageImmune(victim, spellProto->Id);
+        return 0;
+    }
+
     if (victim->IsAIEnabled)
         victim->GetAI()->DamageTaken(this, damage);
 
@@ -2607,10 +2613,6 @@ SpellMissInfo Unit::SpellHitResult(Unit* victim, SpellInfo const* spellInfo, boo
     if (spellInfo->IsPositive() && !IsHostileTo(victim)) // prevent from affecting enemy by "positive" spell
         return SPELL_MISS_NONE;
 
-    // Check for immune
-    if (victim->IsImmunedToDamage(spellInfo))
-        return SPELL_MISS_IMMUNE;
-
     if (this == victim)
         return SPELL_MISS_NONE;
 
@@ -7673,6 +7675,9 @@ bool Unit::IsImmunedToDamage(SpellSchoolMask schoolMask) const
 
 bool Unit::IsImmunedToDamage(SpellInfo const* spellInfo) const
 {
+    if (!spellInfo)
+        return false;
+
     if (spellInfo->HasAttribute(SPELL_ATTR1_UNAFFECTED_BY_SCHOOL_IMMUNE) || spellInfo->HasAttribute(SPELL_ATTR2_UNAFFECTED_BY_AURA_SCHOOL_IMMUNE))
         return false;