Crash after closing the About dialog
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#### Summary:
<!-- Summarize the issue/suggestion concisely: -->
Inkscape crashes after copying debug info and closing the About dialog.
#### Steps to reproduce:
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- open Inkscape
- open About dialog
- copy debug info
- close about dialog
- switch to another application (e.g. Firefox)
#### What happened?
Inkscape crashes with the following backtrace: (could it be related to the new slideshow functionality?)
<pre>
0# Inkscape::Application::crash_handler(int) in /usr/bin/../lib64/inkscape/libinkscape_base.so.1.4.0.0
1# 0x00007F8563A42EB0 in /lib64/libc.so.6
2# Gtk::Widget::get_parent() in /usr/lib64/libgtkmm-3.0.so.1
3# reveal_widget(Gtk::Widget*, bool) in /usr/bin/../lib64/inkscape/libinkscape_base.so.1.4.0.0
4# 0x00007F856807F938 in /usr/bin/../lib64/inkscape/libinkscape_base.so.1.4.0.0
5# 0x00007F8565582A92 in /usr/lib64/libglibmm-2.4.so.1
6# 0x00007F8566717CFA in /usr/lib64/libglib-2.0.so.0
7# 0x00007F85667140B9 in /usr/lib64/libglib-2.0.so.0
8# 0x00007F8566717067 in /usr/lib64/libglib-2.0.so.0
9# g_main_context_iteration in /usr/lib64/libglib-2.0.so.0
10# g_application_run in /usr/lib64/libgio-2.0.so.0
11# main in /usr/bin/inkscape
12# 0x00007F8563A29B77 in /lib64/libc.so.6
13# __libc_start_main in /lib64/libc.so.6
14# _start in /usr/bin/inkscape
</pre>
#### What should have happened?
Inkscape doesn't crash.
#### Version info
<!--
Open 'Help > About' and click on the little bug icon in the bottom right corner that copies the debug information to your clipboard. For command line users, run 'inkscape --debug-info'.
For Inkscape 1.0.2 and older, please manually add the Inkscape Version and Operating System Version. The Inkscape version is listed in the About dialog. For command line users, run 'inkscape -V'
Paste the information in the empty space between the apostrophes below:
-->
```
Inkscape 1.4-beta (407800dcc4, 2024-05-18, custom)
Compile (Run)
GLib version: 2.80.0
GTK version: 3.24.41 (3.24.41)
glibmm version: 2.66.7
gtkmm version: 3.24.9
libxml2 version: 2.12.6
libxslt version: 1.1.39
Cairo version: 1.18.0 (1.18.0)
Pango version: 1.52.2 (1.52.2)
HarfBuzz version: 8.4.0 (8.4.0)
OS version: Slackware 15.0 x86_64 (post 15.0 -current)
```
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issue