Crash closing multipage file with Export dialog docked
<!--
See our full bug reporting guidelines at https://inkscape.org/contribute/report-bugs/
Writing a good bug report will ensure we'll be able to help efficiently. 🙂
-->
#### Summary:
<!-- Summarize the issue/suggestion concisely: -->
Inkscape crashes when the document is closed (not the window) if the file has multiple pages and Export dialog is open
#### Steps to reproduce:
<!-- Describe what you did (step-by-step) so we can reproduce: -->
- open Inkscape
- Create a few pages
- Open Export Dialog, with pages tab active
- Close with Ctrl+W
#### What happened?
Inkscape crashes and closes.
#### What should have happened?
No crash
#### Version info
Inkscape 1.3 (0e150ed6c4, 2023-07-21)
<!--
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:
-->
```
<pre>
0# boost::stacktrace::basic_stacktrace<std::allocator<boost::stacktrace::frame> >::init(unsigned long long, unsigned long long) in libinkscape_base
1# Inkscape::Application::crash_handler(int) in libinkscape_base
2# 0x00007FF6B18421B2 in inkscape
3# _C_specific_handler in ntdll
4# _chkstk in ntdll
5# _RtlRaiseException in ntdll
6# _KiUserExceptionDispatcher in ntdll
7# SPItem::invoke_show(Inkscape::Drawing&, unsigned int, unsigned int) in libinkscape_base
8# Inkscape::UI::Dialog::PreviewDrawing::construct() in libinkscape_base
9# Inkscape::UI::Dialog::PreviewDrawing::construct() in libinkscape_base
10# Glib::IdleSource::dispatch(sigc::slot_base*) in libglibmm_2_4_1
11# _g_source_get_time in libglib_2_0_0
12# _g_clear_list in libglib_2_0_0
13# _g_main_context_check in libglib_2_0_0
14# _g_main_context_iteration in libglib_2_0_0
15# _g_application_run in libgio_2_0_0
16# 0x00007FF6B18437BB in inkscape
17# 0x00007FF6B18412EE in inkscape
18# 0x00007FF6B18413E6 in inkscape
19# _BaseThreadInitThunk in KERNEL32
20# _RtlUserThreadStart in ntdll
</pre>
<details><summary>System info</summary>
Inkscape 1.3 (0e150ed6c4, 2023-07-21)
GLib version: 2.76.4
GTK version: 3.24.38
glibmm version: 2.66.6
gtkmm version: 3.24.7
libxml2 version: 2.11.4
libxslt version: 1.1.38
Cairo version: 1.17.7
Pango version: 1.50.14
HarfBuzz version: 8.0.1
OS version: Windows 10 22H2
</details>
```
<!--
❤️ Thank you for filling in a new bug report, we appreciate the help! ❤️
Please be patient while we try to find the time to look into your issue.
Remember that Inkscape is developed by volunteers in their spare time, we'll try our best to respond to all reports.
-->
<!--
Please be careful when/after writing # for example in logs, code, or versions of linux
- use inline code span - single backticks (`) before and after it, like this - `#1618`
- use multi-line code block - triple backticks (```) to fence/enclose console logs
- attach long logs as a text file.
-->
issue