I can confirm that it is indeed a bug. If you open the Sources pane in the Property Dialog. The bug causes the program to close if you double-click in the Source Citation List in the area below all listed rows, if any, in this list. The same bug unfortunately affects not just the source citation list, but most other record lists in the program. For example, it will happen if you open the Record Links window (View > Record Links), scroll to the bottom of the list, and double-click in the area below all listed rows. It can even occur in the Records Window - but again, it will only happen if you scroll right to the bottom of the list and double-click in the white space below the last row.
Some people have said that the bug will occur if you just double-click on the background of the list. I suppose it depends what you mean by 'background'. It is not the case that it will happen if you just double-click in any unused (no text) area within the list. You have to scroll past the end of all listed records and double click below them. And it won't happen anywhere in the list if you just single-click.
I do apologise for this bug. We will shortly be issuing a patch that will fix it.
Simon Orde
List Administrator & Family Historian designer
* Program Crash when Clicking on White Space
Program Crash when Clicking on White Space
Update 2.2.3 corrects this problem