Most floating dialogs not opening at all (1.2-dev)
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#### Steps to reproduce:
<!-- Describe what you did (step-by-step) so we can reproduce: -->
- open Inkscape
- open xml editor
- open document properties
- open filter editor
- open fill and stroke
- open symbols
#### What happened?
**Working**: Document Properties, Preferences, About, and non-floating dialogs
**Not working**: Input devices, XML Editor, Filter editor
#### What should have happened?
All of the listed dialogs should have opened.
Files:

#### Inkscape Version and Operating System:
Inkscape 1.2-dev (inkscape@da2df6f5a3bc801c54284fddf3856e0c56dc710e, 2021-07-26)
GLib version: 2.68.0
GTK version: 3.24.29
glibmm version: 2.60.0
gtkmm version: 3.24.4
libxml2 version: 2.9.12
libxslt version: 1.1.34
Cairo version: 1.16.0
Pango version: 1.48.4
HarfBuzz version: 2.8.0
OS version: macOS 11.4
issue