Fix collapseAll command when no folder is open

[tomheaton]

Description

This PR adds a null check before casting a view to ExplorerView and running collapseAll, to avoid a potential TypeError when the view is null.

Changes Made

I added a check for null before casting to ExplorerView and running collapseAll, as shown in this code snippet:

if (view !== null) {
  const explorerView = view as ExplorerView;
  explorerView.collapseAll();
}

Testing Done

I tested this change in Code OSS dev, both with and without the changed code, to verify that the view is properly collapsed when it is not null.

Screenshots

Error Message Before Fix

Fix in Action

no error message

[lramos15]

Thanks!

[lramos15]

Do we want if (view) to cover null and undefined?

[tomheaton]

since the type of view is IView | null I didn't think so

[tomheaton]

(normally I would do that but because big codebase I wanted it to be an explicit check to avoid confusion)