Spins in repaint_phyrect due to 0-width cell

[James McCoy]

I don't exactly recall the situation that led to this. I think it was related to resizing the terminal while less was active and then when quitting less pangoterm got stuck in this loop:

 828 for(ph_pos.pcol = ph_rect.start_pcol; ph_pos.pcol < ph_rect.end_pcol; ) {
 829 VTermPos pos = VTERMPOS_FROM_PHYSPOS(pt, ph_pos);
 830
 831 VTermScreenCell cell;
 832 fetch_cell(pt, pos, &cell);
...
 895 ph_pos.pcol += cell.width;
 896 }

It seems like this was the last column, if that's relevant, since setting cell.width to 1, in the debugger, just before line 895 executed caused the loop to terminate.