Clear diff in history form when clicked on empty area, just like main form and commit form do

[mast-eu]

Feature description

Currently there are 2 different strategies for dealing with clicks on empty areas when showing diffs.

The main form unselects the file and clears the diff view:

The commit form does the same like the main form:

However, the history form behaves slightly differently. Clicking the empty area still de-selects the file, but the diff view is not cleared.

The behaviour should be aligned to the other two forms. This has been discussed in
#6231 .

Environment

GitExtensions 3.

[gerhardol]

Agree this should be changed