MSA overview: black area in exported image

I.
1. Open COI.aln.
2. MSA Overview: right click -> Export as image.
3. Uncheck "Export graph overview".
4. Export.
=> There is a black area in the bottom of the exported image.

II.
The same thing happens when you uncheck the other checkbox, but the black area is in the top of the picture.

III.
Also, it is possible to uncheck the both checkboxes. In this case the black image is exported.