Toolbar (e.g. command bar) toggle show/hidden states are not preserved during the fullscreen transition
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#### Summary:
<!-- Summarize the issue/suggestion concisely: -->
Toolbar (e.g. command bar) toggle show/hidden states are not preserved during the fullscreen transition.
From the behavior, it seems that there are separate boolean variables for the normal mode / fullscreen mode,
and the variables are not synchronized during the screen transition.
#### Steps to reproduce:
- open Inkscape (assuming the vanilla state)
- hide the command bar from the View->Show/Hide menu
- go to the fullscreen mode
#### What happened?
- the command bar erroneously appears
- if you open the View->Show/Hide menu, the checkbox is off, indicating hidden; but the bar is shown
- if you further toggle the checkbox; now the checkbox is on, indicating shown; then the bar is hidden
#### What should have happened?
the toggle state should be preserved during the screen transitions
Sample attachments: video showing the similar behavior in the opposite situation:
Go from (hidden, fullscreen) -> (hidden, normal), but the bar gets shown

#### Version Info:
```
- Inkscape Version: Inkscape 1.0 (4035a4fb49, 2020-05-01)
- Operating System: Fedora 32 with Cinnamon desktop
- Operating System version: Linux 5.7.11-200.fc32.x86_64 (from uname)
```
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issue