Regression: Click on file while other files are selected should select only the clicked file

Bug exists in thunar 4.15.2, but not in 4.15.1

Just did a quick git bisect sesssion, and found out that a4743261 is the culprit.

@reubengreen73, you have time to take a look into it ?

(Edit: its a4743261, not 5992d236)