fix: add null-tolerant length checks (AscensionGameDev#1998)

* fix: add null-tolerant length check

* fix: null-tolerant lookup

Author: pandinocoder

Intersect (Core)/GameObjects/ItemBase.cs

@@ -376,9 +376,8 @@ public static ItemBase[] GetCooldownGroup(string cooldownGroup)
                 return Array.Empty<ItemBase>();
             }
 
-            return Lookup
-                .Where(i => ((ItemBase)i.Value).CooldownGroup.Trim() == cooldownGroup)
-                .Select(i => (ItemBase)i.Value)
+            return Lookup.Values.OfType<ItemBase>()
+                .Where(descriptor => descriptor.CooldownGroup?.Trim() == cooldownGroup)
                 .ToArray();
         }
 

Intersect.Server.Core/Entities/Player.cs

@@ -6719,7 +6719,7 @@ public void UpdateCooldown(ItemBase item)
             }
 
             // Are we dealing with a cooldown group?
-            if (item.CooldownGroup.Trim().Length > 0)
+            if (!string.IsNullOrWhiteSpace(item.CooldownGroup))
             {
                 // Yes, so handle it!
                 UpdateCooldownGroup(GameObjectType.Item, item.CooldownGroup, item.Cooldown, item.IgnoreCooldownReduction);