Core/Spells: fixed power check for runes when casting spells - these have their own check and don't require the default one

(cherry picked from commit 7f29956937)

src/server/game/Spells/Spell.cpp

@@ -7507,6 +7507,8 @@ SpellCastResult Spell::CheckPower() const
             SpellCastResult failReason = CheckRuneCost();
             if (failReason != SPELL_CAST_OK)
                 return failReason;
+
+            continue;
         }
 
         // Check power amount