composing indications in vertical and horizontal tab list differ

Steps to reproduce

1. Using the following config options:
   enable_vertical_tab_list False
2. Compose a message in tabA and don't send it
3. Switch to tabB
4. /set enable_vertical_tab_list True

Expected behaviour

The list of tabs displayed in the vertical or horizontal mode are the same.

What happens

The composing tabA is not shown in the horizontal mode but it is in the vertical mode.

Misc

This is independent of show_composing_tabs, which is for received chatstates. I have this to False here.