Compare project to perforce.
Select a different file, fileA.txt, and click "History".
Select another file - one with a "?" icon (A file not in the depot nor in the project).
BUG: The History window is disabled, yet it continues to show information for FileA.txt.
Select another different file, say FileB.txt.
In the history diff window (still showing information for FileA), select a revision and use the Diff dropdown to compare version #3 to version #4.
History correctly shows the diff for FileA.txt