Core/Spells: Don't allow passive area auras to stack.

src/server/game/Spells/Auras/SpellAuras.cpp

@@ -856,6 +856,16 @@ void Aura::RefreshSpellMods()
             player->RestoreAllSpellMods(0, this);
 }
 
+bool Aura::IsArea() const
+{
+    for (uint8 i = 0; i < MAX_SPELL_EFFECTS; ++i)
+    {
+        if (HasEffect(i) && GetSpellInfo()->Effects[i].IsAreaAuraEffect())
+            return true;
+    }
+    return false;
+}
+
 bool Aura::IsPassive() const
 {
     return GetSpellInfo()->IsPassive();
@@ -1865,7 +1875,8 @@ bool Aura::CanStackWith(Aura const* existingAura) const
     // spell of same spell rank chain
     if (m_spellInfo->IsRankOf(existingSpellInfo))
     {
-        if (m_spellInfo->IsMultiSlotAura())
+        // don't allow passive area auras to stack
+        if (m_spellInfo->IsMultiSlotAura() && !IsArea())
             return true;
         if (GetCastItemGUID() && existingAura->GetCastItemGUID())
             if (GetCastItemGUID() != existingAura->GetCastItemGUID() && (m_spellInfo->AttributesCu & SPELL_ATTR0_CU_ENCHANT_PROC))