Crash when running Nyquist Prompt with code that has widgets

[SteveDaulton]

Describe the bug Running any code in the Nyquist Prompt that includes a ";control" widget crashes Audacity

To Reproduce Minimal example - apply the following code in the Nyquist Prompt to a selection in an audio track:

;control dummy "Dummy control" int "" 5 0 10
(noise)

Actual behavior Audacity crashes.

Expected behavior White noise returned to the selected region

Screenshots If applicable, add screenshots/video to help explain your problem.

Additional information (please complete the following information):

• OS: Any
• Version Audacity 3.2.0 alpha

Additional context Regression. ../source_subfolder/src/common/wincmn.cpp(1492): assert ""firstHandler->GetPreviousHandler() == __null"" failed in PopEventHandler(): the first handler of the wxWindow stack should have no previous handlers set

[Ryan-Miller-Audacity]

I was able to reproduce this as described.

Here is a link to the sentry report for the crash as well: https://sentry.audacityteam.org/share/issue/56dc4b54c3024710903a5aade0bf4149/

[Paul-Licameli]

I have made an alternative fix to Dmitry's, which is surprisingly simple, though I took some wrong turns finding it.