Enforce debug content when EditorModel is invalid

[colin-grant-work]

What it does

Fixes #10159 by enforcing the addition of content when the editor is in an invalid state.

How to test

1. Create a .theia/launch.json by clicking the Add Configuration... button on theRun menu.
2. Delete the .theia folder manaually and close the editor.
3. Click the Add Configuration menu item again.
4. Observe that an editor is opened with the skeleton of the launch configuration.

Review checklist

• As an author, I have thoroughly tested my changes and carefully followed the review guidelines

Reminder for reviewers

• As a reviewer, I agree to behave in accordance with the review guidelines

Signed-off-by: Colin Grant colin.grant@ericsson.com

[msujew]

I can confirm that the issue exists on master and the changes address it nicely 👍