For #81574

Fixes #81788

These checks should not be required now that we have strict null checking enabled

TS 3.7 changes the many dom style typings to just be `string` instead of `string | null`. Use empty string in place of null for these cases

This reverts commit d591cb7e.

Fixes #81889

Using `.matches` can cause a custom editor to match all custom editors for that resource. Use a strict compare instead.

Fixes #81884

Fixes #80680

- Always sync the current preview line number with the editor, even when `scrollEditorWithPreview` is false

- If the md file is focused and refresh is called, do not try resetting the current line to match the editor file. This mainly effects the case where `scrollEditorWithPreview` is false

Fixes #81791

microsoft/vscode-remote-release#1598

Fixes https://github.com/microsoft/vscode/issues/81767

Fixes https://github.com/microsoft/vscode-remote-release/issues/980

WSL window opening with windows path.  Fixes https://github.com/microsoft/vscode-remote-release/issues/1537

If there is an error while resolving the webview itself, this invisible container can end sticking around incorrectly until the input it destoryed. Better to make sure it is hidden so that it doesn't block user input