Remove items that don't have a material from the tool grid.

fixes #1353

src/items.zig

@@ -520,6 +520,7 @@ pub const Tool = struct { // MARK: Tool
 		var items: [25]?*const BaseItem = undefined;
 		for(&items, 0..) |*item, i| {
 			item.* = reverseIndices.get(zonArray.getAtIndex([]const u8, i, "null"));
+			if(item.* != null and item.*.?.material == null) item.* = null;
 		}
 		return items;
 	}