bug#73022: 31.0.50; Crash in build_frame_matrix_from_leaf_window after C-x 2 and reducing terminal size

[Daniel Clemente <n142857@gmail.com>]

> I noticed that causing this assertion to fail is not very easy.  For
> example, if I drag the terminal emulator window one line at a time, I
> can never cause it, even if I get to frame sizes that are much smaller
> than the minimum we need for 2 windows.  Somehow, I need to drag the
> frame so it resizes by several lines and/or columns.  Not sure why.
>

I can cause the build_frame_matrix_from_leaf_window failed assertion (
  glyph_row_slice_p(window_row, frame_row) is false  ) when slowly
resizing row by row (7→6→5 rows). The number of columns doesn't matter
(can be a normal one).

You can also try maximizing/unmaximizing“the window if you window
manager supports it. That's a way of suddenly changing the number of
rows from a normal value (e.g. 20) to a dangerous value (e.g. 4).
After unmaximizing it immediately crashes (if you did the C-x 2
split).