Missing element event_date for upcoming stream results in TypeError

[cas--]

Describe the bug

Last weekend trying to list the WRC event encountered an error:

TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

This was due to element missing event_date attribute (see pdb_locals)

The quick fix is to fallback with empty string:

-    list_item.setPath('/notify/' + localize(30024), localize(30025), element.get('event_date') + ' (GMT+' + str(timezone / 3600 * -1))
+    list_item.setPath('/notify/' + localize(30024), localize(30025), element.get('event_date', '') + ' (GMT+' + str(timezone / 3600 * -1))

To Reproduce

Steps to reproduce the behavior:

1. Go to Events -> Upcoming Live Events -> FIA World Rally Championship -> Schedule

Expected behavior

Listing of all scheduled videos for the event, usually one for Friday, Saturday and Sunday.

Additional context

• Operating system: NixOS
• Kodi version: 20
• Addon version: 3.2.2

Log (if available)

Error Type: <class 'TypeError'>
Error Contents: unsupported operand type(s) for +: 'NoneType' and 'str'
Traceback (most recent call last):
  File "/var/lib/kodi/addons/plugin.video.redbull.tv/resources/lib/addon_entry.py", line 10, in <module>
    run(argv)
  File "/var/lib/kodi/addons/plugin.video.redbull.tv/resources/lib/addon.py", line 221, in run
    plugin.run(params)
  File "/var/lib/kodi/addons/script.module.routing/lib/routing.py", line 130, in run
    self._dispatch(self.path)
  File "/var/lib/kodi/addons/script.module.routing/lib/routing.py", line 141, in _dispatch
    view_func(**kwargs)
  File "/var/lib/kodi/addons/plugin.video.redbull.tv/resources/lib/addon.py", line 120, in browse_collection
    build_menu(redbull.get_collection_url(uid))
  File "/var/lib/kodi/addons/plugin.video.redbull.tv/resources/lib/addon.py", line 165, in build_menu
    list_items.append(generate_list_item(item, PRODUCT))
                      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/var/lib/kodi/addons/plugin.video.redbull.tv/resources/lib/addon.py", line 194, in generate_list_item
    list_item.setPath('/notify/' + localize(30024), localize(30025), element.get('event_date') + ' (GMT+' + str(timezone / 3600 * -1))
                                                                    ~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~
TypeError: unsupported operand type(s) for +: 'NoneType' and 'str'

[cas--]

I can provide a more comprehensive fix via PR when I get a bit of free time