[7.13.0] TypeError: 'NoneType' object is not subscriptable in StartDownloadDialog.__init__()

[kozlovsky]

tribler.gui.utilities.CreationTraceback:
  File "run_tribler.py", line 115, in <module>
  File "tribler\gui\start_gui.py", line 58, in run_gui
  File "tribler\gui\tribler_app.py", line 32, in __init__
The above exception was the direct cause of the following exception:
Traceback (most recent call last):
  File "tribler\gui\utilities.py", line 438, in trackback_wrapper
  File "tribler\gui\utilities.py", line 435, in trackback_wrapper
  File "tribler\gui\tribler_app.py", line 36, in on_app_message
  File "tribler\gui\tribler_app.py", line 40, in handle_uri
  File "tribler\gui\tribler_window.py", line 1256, in handle_uri
  File "tribler\gui\tribler_window.py", line 639, in process_uri_request
  File "tribler\gui\tribler_window.py", line 866, in start_download_from_uri
  File "tribler\gui\dialogs\startdownloaddialog.py", line 100, in __init__
TypeError: 'NoneType' object is not subscriptable

Here:

        self.dialog_widget.anon_download_checkbox.setChecked(
            self.window().tribler_settings['download_defaults']['anonymity_enabled']

It looks like sometimes an option can be missed from the config.

[sentry-for-tribler]

Sentry issue: TRIBLER-1E2

[drew2a]

I can not reproduce the bug but I have a hypnotise of how it could happened.

Consider the following sequence:

1. Tribler starts the second instance of GUI and receives a URL from the first instance via the local socket (you can see it in logs)
2. GUI handles the URL:
   

   tribler/src/tribler/gui/tribler_window.py

   Lines 1253 to 1256 in 5662d71

   	def handle_uri(self, uri):
   	self.pending_uri_requests.append(uri)
   	if self.tribler_started and not self.start_download_dialog_active:
   	self.process_uri_request()

But there is a chance that at this moment self.tribler_settings is still None as they have not been received yet. Therefore we see the TypeError: 'NoneType' object is not subscriptable as self.tribler_settings equals None.