When pressing F1 in source, and help is not found, documentation pane shows "No documentation available". Still, the help pane gets focus, even though it makes no sense.

In that case focus should stay in the editor.

Additionally, pressing ESC once should probably close the help pane, as it contains no useful information. If help pane was already open, pressing ESC in that situation could also go to previous valid help page.

(Additional suggestion: the "No documentation available" text could be "No documentation available for <what the help was searched for>".)