Guake not reachable anymore when you put wrong command for startup

**Describe the bug**

I wanted guake to hook on the command when starting up for first time, called `tmux attach`.

Seems this was the wrong command, but I'm not able either to adjust/correct the command. Traceback:

```
Guake not running, starting it
Loading Gnome schema from: /usr/share/glib-2.0/schemas
Language previously loaded from: /usr/share/locale
Guake Terminal 3.10
VTE 0.68.0
Gtk 3.24.33
created fresh notebook for workspace 0
Spawning new terminal at /home/ehart
current workspace is 0
System doesn't support transparency
can't bind show-focus key
Spawning new terminal at /home/ehart
Guake tabs restored from /home/ehart/.config/guake/session.json
Guake initialized
Calling startup script: tmux attach
Traceback (most recent call last):
File "/usr/bin/guake", line 33, in
sys.exit(load_entry_point('guake==3.10', 'console_scripts', 'guake')())
File "/usr/lib/python3/dist-packages/guake/main.py", line 664, in exec_main
if not main():
File "/usr/lib/python3/dist-packages/guake/main.py", line 646, in main
pid = subprocess.Popen( # pylint: disable=consider-using-with
File "/usr/lib/python3.10/subprocess.py", line 971, in __init__
self._execute_child(args, executable, preexec_fn, close_fds,
File "/usr/lib/python3.10/subprocess.py", line 1863, in _execute_child
raise child_exception_type(errno_num, err_msg, err_filename)
FileNotFoundError: [Errno 2] No such file or directory: 'tmux attach'
```
Okay, no problem. Then I should be able to modify the startup script at hook of Guake start.

Then Guake Preferences binary doesn't open anymore. Killing Guake and trying, but Guake Preferences window is not reachable.

Then I searched everywhere in Guake config or settings, but nowhere the command `tmux attach` is set somewhere. But yet everytime when I start, Guake, Guake seems to be able to read the command `tmux attach` somewhere, which isn't clear where.

As fallback, I tried
guake --restore-preferences my_old_preferences

But alas, I keep getting the same error when starting guake, and can't find out where I can adjust it.

**Expected behavior**

If the command is wrong, Guake Preferences window should be able to reachable to correct the mistake.

**To Reproduce**

Add `tmux attach` in Guake command hooks, at start up. And then restart Guake.

------------------------------------------------------------------------------

Guake Version: 3.10

Vte Version: 0.68.0

Vte Runtime Version: 0.68.0

--------------------------------------------------
GTK+ Version: 3.24.33

GDK Backend: