Bug#931467: reportbug-gtk: Crashes after setting package name

[David <david@librem.one>]

Package: reportbug-gtk
Version: 7.5.2
Severity: important

Dear Maintainer,

*** Reporter, please consider answering these questions, where appropriate ***

   * What led up to the situation? Started reportbug-gtk and attempted to log bug.

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

      * Started reportbug-gtk
      * Entered package name
      * Clicked "Next"
      * Got message "Checking for newer versions at madison..."

   * What was the outcome of this action? Crashed with:

```
Traceback (most recent call last):
  File "/usr/bin/reportbug", line 2285, in <module>
    main()
  File "/usr/bin/reportbug", line 1115, in main
    return iface.user_interface()
  File "/usr/bin/reportbug", line 1728, in user_interface
    latest_first=self.options.latest_first)
  File "/usr/lib/python3/dist-packages/reportbug/ui/gtk_ui.py", line 1763, in func
    args, kwargs = op.sync_pre_operation(*args, **kwargs)
TypeError: cannot unpack non-iterable NoneType object
```

   * What outcome did you expect instead? Next step in reportbug process.

*** End of the template - remove these template lines ***


-- System Information:
Distributor ID:	PureOS
Description:	PureOS
Release:	8
Codename:	green
Architecture: x86_64

Kernel: Linux 4.19.0-5-amd64 (SMP w/4 CPU cores)
Kernel taint flags: TAINT_WARN
Locale: LANG=en_US.UTF-8, LC_CTYPE=en_US.UTF-8 (charmap=UTF-8), LANGUAGE=en_US.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages reportbug-gtk depends on:
ii  gir1.2-gtk-3.0         3.24.5-1
ii  gir1.2-vte-2.91        0.54.2-2
ii  python3-gi             3.30.4-1
ii  python3-gi-cairo       3.30.4-1
ii  python3-gtkspellcheck  4.0.5-1
ii  reportbug              7.5.2

reportbug-gtk recommends no packages.

reportbug-gtk suggests no packages.

-- no debconf information