fix KeyError exception triggered on closing a window

[rchl]

wm.destroy is called in two cases:

• from EventListener.on_pre_close_window, before the window is closed
• from plugin_unloaded hook when LSP package is unloaded

The changed line is triggered in the former case.

As the comment in WindowManager.destroy() says, we should (have to!) call it from the main thread when the plugin is unloaded. But afaics, we don't need to call it from the main thread when closing a window so change the code to not do that.

Calling it from the main thread on window closing triggers a KeyError exception due to DocumentListener.on_close being triggered first and DocumentListener.on_session_shutdown_async later. The latter removes session view from the main thread first and the former tries to remove it again from scheduled execution on the async thread.

Fixes #2399

[predragnikolic]

Not that related to the PR,
but I have a question,

If you have multiple ST windows, and invoke WindowRegistry.disable, that will nuke all WindowManagers from all ST windows?
If you have multiple ST windows, and invoke WindowRegistry.discard, that will discard only the WindowManager for one ST window?

... I am trying to figure out the difference and consequence of disable and discard.

[rchl]

Yeah, as you said. The discard function takes a window argument while disable doesn't.

[samirbajaj]

Thank you @rchl for fixing this issue -- much appreciated!

Reviewers -- please approve and merge. Thank you.

[predragnikolic]

I was only able to reproduce it in safe mode.

I cannot reproduce the exception with this PR.