[Wa] Last paragraph is duplicated when deleted; editor scrolls in loop

A paragraph is a slice of sequences and a consensus displayed in the multiline mode.

1. Open COI.aln in the multiline mode.
2. Rewind the alignment down.
3. Select all sequences in the last paragraph.
4. Press Delete.
   Expected: the entire paragraph has been deleted successfully.
   Current state: the paragraph starting at character 505 is duplicated.
5. Scroll to bottom.
   The paragraphs have been updated.
6. Repeat steps 3—5 until the entire alignment is selected in the Overview.
7. Delete the last paragraph for the last time and scroll the mouse wheel down.
   Current state: scrolling cannot stop at the end, the scrollbar appears at the beginning and loops.