*Fix dispel chance mod calculation.

*Fix Escape artist-by Lightguard.

--HG--
branch : trunk

src/game/SpellAuras.cpp

@@ -5066,6 +5066,21 @@ void Aura::HandleShapeshiftBoosts(bool apply)
     m_target->SetHealth(uint32(ceil((double)m_target->GetMaxHealth() * healthPercentage)));*/
 }
 
+bool Aura::GetDispelChance(Spell* spell)
+{
+    // we assume that aura dispel chance is 100% on start
+    // need formula for level difference based chance
+    int32 miss_chance = 100;
+    // Apply dispel mod from aura caster
+    if (Unit *caster = GetCaster())
+    {
+        if ( Player* modOwner = caster->GetSpellModOwner() )
+            modOwner->ApplySpellMod(GetId(), SPELLMOD_RESIST_DISPEL_CHANCE, miss_chance, spell);
+    }
+    // Try dispel
+    return roll_chance_i(miss_chance);
+}
+
 void Aura::HandleAuraEmpathy(bool apply, bool Real)
 {
     if(m_target->GetTypeId() != TYPEID_UNIT)