Remove bindings to/from justpy elements which are already deleted

nicegui.code-workspace

@@ -19,6 +19,13 @@
   "launch": {
     "version": "0.2.0",
     "configurations": [
+      {
+        "name": "current file",
+        "type": "python",
+        "request": "launch",
+        "program": "${file}",
+        "console": "integratedTerminal"
+      },
       {
         "name": "Dockerized NiceGUI",
         "type": "python",

nicegui/binding.py

@@ -11,13 +11,17 @@ async def loop():
     while True:
         visited = set()
         invalidated_views = []
-        for source_obj, source_name, target_obj, target_name, transform in active_links:
+        for link in active_links[:]:
+            (source_obj, source_name, target_obj, target_name, transform) = link
             value = transform(getattr(source_obj, source_name))
             if getattr(target_obj, target_name) != value:
                 setattr(target_obj, target_name, value)
                 propagate(target_obj, target_name, visited)
                 if hasattr(target_obj, 'view') and isinstance(target_obj.view, HTMLBaseComponent):
                     invalidated_views.append(target_obj.view)
+            # remove links if the justpy element has been deleted
+            if getattr(target_obj, 'delete_flag', False) or getattr(source_obj, 'delete_flag', False):
+                active_links.remove(link)
         for view in invalidated_views:
             await view.update()
         await asyncio.sleep(0.1)