Fix a bug with `:Hgstatus` showing diff summaries in its own window. This could happen when the user would commit from the status window, and do a `:Hgstatusvdiffsum` right away. It wouldn't find the previous window because it would be gone (the commit message window), so it would split the status window itself, which is often too small. Now Lawrencium tries to avoid picking the status window itself, and will just find any other window instead.