Bug#1018026: meld: del key does not work in git dir-diff mode

[Vilius Panevėžys]

Package: meld
Version: 3.20.2-2
Severity: normal

   * What led up to the situation?

	0. `cd` to a Git working copy with at least one modified file.
	1. Run `git difftool -d -t meld`.
	2. Open a modified file.
	3. Press the "delete" key on the keyboard.

   * What was the outcome of this action?

   The character to the left of the cursor not deleted, the following
   error is printed to stderr.

	Traceback (most recent call last):
	  File "/usr/lib/python3/dist-packages/meld/dirdiff.py", line 1260, in on_button_delete_clicked
		self.delete_selected()
	  File "/usr/lib/python3/dist-packages/meld/misc.py", line 54, in wrap_function
		return function(args[0], pane, *args[1:], **kwargs)
	  File "/usr/lib/python3/dist-packages/meld/dirdiff.py", line 1024, in delete_selected
		paths = self._get_selected_paths(pane)
	  File "/usr/lib/python3/dist-packages/meld/dirdiff.py", line 1308, in _get_selected_paths
		assert pane is not None
	AssertionError

   * What outcome did you expect instead?

   The character to the left of the cursor deleted, no errors.

When invoked with `git difftool -t meld`, "delete" key works as
expected - the problem is only reproducible in dir-diff mode.

-- System Information:
Debian Release: 11.4
  APT prefers stable-security
  APT policy: (500, 'stable-security'), (500, 'stable')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 5.10.0-17-amd64 (SMP w/4 CPU threads)
Locale: LANG=en_US.utf8, LC_CTYPE=en_US.utf8 (charmap=UTF-8), LANGUAGE=en_US:en
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)
LSM: AppArmor: enabled

Versions of packages meld depends on:
ii  dconf-gsettings-backend [gsettings-backend]  0.38.0-2
ii  gir1.2-gtksource-3.0                         3.24.11-2
ii  libcanberra-gtk3-module                      0.30-7
ii  libgtk-3-0                                   3.24.24-4+deb11u2
ii  libgtksourceview-3.0-1                       3.24.11-2
ii  patch                                        2.7.6-7
ii  python3                                      3.9.2-3
ii  python3-cairo                                1.16.2-4+b2
ii  python3-gi                                   3.38.0-2
ii  python3-gi-cairo                             3.38.0-2

Versions of packages meld recommends:
ii  yelp  3.38.3-1

meld suggests no packages.

-- no debconf information