0.9.1 regression: clicking delete in preview window does not advance to next message

[kswartz26]

This bug was just introduced, reproduced in Firefox 52 ESR. When you open the preview window and click the icon to delete a message, it does delete it, but the preview window does not update. It neither moves to the next message, nor updates the message counter. Workaround is to close the preview window and open it again.