"Zoom out" button is not updated in Sequence view

1.

{ File -> New document from text... }

Expected state: the "Create document" dialog has appeared
2. Set sequence "AAAA", set some valid document path and click "Create".
Expected state: the Sequence view has opened, the "Zoom out" button is disabled.
3. Call context menu

{ Edit sequence -> Insert subsequence... }

Expected state: the "Insert Sequence" dialog has appeared
4. Set sequence "AAAA", position to insert - 5 and click "OK".
Expected state: the same sequence region is displayed, scrollbar has shrunk, "Zoom out" has enabled.
Current state: all is correct except that "Zoom out" remains inactive. However, it becomes enabled if sequence view scrollbar is moved.