Check for Unbreakable tag before handling durability changes

Unsure if this is the best way to stop durability loss when an item is
Unbreakable, or if this should be checked before each call to
handleDurabilityChange.

src/main/java/com/gmail/nossr50/util/skills/SkillUtils.java

@@ -177,8 +177,10 @@ public class SkillUtils {
     }
 
     public static void handleDurabilityChange(ItemStack itemStack, int durabilityModifier) {
+        if (!itemStack.isUnbreakable()) {
             handleDurabilityChange(itemStack, durabilityModifier, 1.0);
         }
+    }
 
     /**
      * Modify the durability of an ItemStack.