fix toolbelt slot group

Author: ghzdude

src/main/java/gregtech/api/items/toolitem/ItemGTToolbelt.java

@@ -115,7 +115,7 @@ public ModularPanel buildUI(HandGuiData guiData, PanelSyncManager guiSyncManager
 
         int heightBonus = (handler.getSlots() / 9) * 18;
 
-        SlotGroup group = new SlotGroup("toolbelt_inventory", 9);
+        SlotGroup group = new SlotGroup("toolbelt_inventory", Math.min(handler.getSlots(), 9));
         guiSyncManager.registerSlotGroup(group);
 
         List<ItemSlot> slots = new ArrayList<>();