Fix immunity system for many spells.

src/server/game/Spells/Spell.cpp

@@ -1562,7 +1562,7 @@ SpellMissInfo Spell::DoSpellHitOnUnit(Unit* unit, const uint32 effectMask, bool
     }
 
     for (uint32 effectNumber = 0; effectNumber < MAX_SPELL_EFFECTS; ++effectNumber)
-        if (effectMask & (1 << effectNumber))
+        if (effectMask & (1 << effectNumber) && !unit->IsImmunedToSpellEffect(m_spellInfo, effectNumber)) //Handle effect only if the target isn't immune.
             HandleEffects(unit, NULL, NULL, effectNumber, SPELL_EFFECT_HANDLE_HIT_TARGET);
 
     return SPELL_MISS_NONE;

src/server/game/Spells/SpellInfo.cpp

@@ -1755,6 +1755,14 @@ Mechanics SpellInfo::GetEffectMechanic(uint8 effIndex) const
     return MECHANIC_NONE;
 }
 
+bool SpellInfo::HasAnyEffectMechanic() const
+{
+    for (uint8 i = 0; i < MAX_SPELL_EFFECTS; ++i)
+        if (Effects[i].Mechanic)
+            return true;
+    return false;
+}
+
 uint32 SpellInfo::GetDispelMask() const
 {
     return GetDispelMask(DispelType(Dispel));

src/server/game/Spells/SpellInfo.h

@@ -446,6 +446,7 @@ public:
     uint32 GetEffectMechanicMask(uint8 effIndex) const;
     uint32 GetSpellMechanicMaskByEffectMask(uint32 effectMask) const;
     Mechanics GetEffectMechanic(uint8 effIndex) const;
+    bool HasAnyEffectMechanic() const;
     uint32 GetDispelMask() const;
     static uint32 GetDispelMask(DispelType type);
     uint32 GetExplicitTargetMask() const;