Motivation / Problem

@ldpl found a nice crash with SDL. We finally know why we had to reset the dirty-rects! :D

Left a proper comment for future-us, instead of a comment that nobody understood.

Description

During resizing, there can still be dirty-rects ready to blit based
on the old dimensions. X11 with shared memory enabled crashes if
you try to do this. So, instead, if we resize, reset the dirty-rects.

This is fine, as moments later we mark the whole (new) screen as
dirty anyway.

Limitations

Checklist for review

Some things are not automated, and forgotten often. This list is a reminder for the reviewers.

• The bug fix is important enough to be backported? (label: 'backport requested')
• This PR affects the save game format? (label 'savegame upgrade')
• This PR affects the GS/AI API? (label 'needs review: Script API')
  • ai_changelog.hpp, gs_changelog.hpp need updating.
  • The compatibility wrappers (compat_*.nut) need updating.
• This PR affects the NewGRF API? (label 'needs review: NewGRF')
  • newgrf_debug_data.h may need updating.
  • PR must be added to API tracker