Core/Spells: Don't grant runic power when death knight abilities that do it using negative power cost miss and the spell has SPELL_ATTR1_DISCOUNT_POWER_ON_MISS

Author: Shauren

src/server/game/Spells/Spell.cpp

@@ -5572,6 +5572,11 @@ void Spell::TakePower()
     {
         if (!hit)
         {
+            // skipping granting power through negative cost only when spell has SPELL_ATTR1_DISCOUNT_POWER_ON_MISS is correct behavior
+            // tested with 206931 - Blooddrinker
+            if (cost.Amount < 0)
+                continue;
+
             //lower spell cost on fail (by talent aura)
             if (Player* modOwner = unitCaster->GetSpellModOwner())
                 modOwner->ApplySpellMod(m_spellInfo, SpellModOp::PowerCostOnMiss, cost.Amount);