Double setting dialog opened

[CyrilleB79]

Issue opened after #12800 (comment).
Cc @seanbudd

Steps to reproduce:

• Open braille settings
• press "Change button to choose braille display
• focus desktop (windows+D)
• press NVDA+ctrl+V to open voice settings

Actual behavior:

New dialog opens and the following error is logged:

IO - external:inputCore.executeGesture (15:08:06.965) - winInputHook (10856):
Input: kb(desktop):NVDA+control+v
DEBUG - external:gui.settingsDialogs.__new__ (15:08:07.004) - MainThread (11064):
Creating new settings dialog (multiInstanceAllowed:False). State of _instances {<gui.settingsDialogs.NVDASettingsDialog object at 0x1255FD50>: <DialogState.DESTROYED: 1>, <gui.settingsDialogs.BrailleDisplaySelectionDialog object at 0x1260B760>: <DialogState.CREATED: 0>}
ERROR - external:gui.settingsDialogs.__new__ (15:08:07.004) - MainThread (11064):
Opening new settings dialog while instance still exists: <gui.settingsDialogs.NVDASettingsDialog object at 0x1255FD50>

Expected behavior:

Only one setting dialog should be able to open at a time.

System configuration

NVDA installed/portable/running from source:

installed

NVDA version:

2021.2rc1

Windows version:

Windows 10 20H2 (64-bit) build 19042.1165

Name and version of other software in use when reproducing the issue:

N/A

Other information about your system:

N/A

Other questions

Does the issue still occur after restarting your computer?

yes

Have you tried any other versions of NVDA? If so, please report their behaviors.

No but probably not new

If add-ons are disabled, is your problem still occurring?

Yes

Does the issue still occur after you run the COM Registration Fixing Tool in NVDA's tools menu?

Not tested.