Smooth plugins are not finishing up

[DominusExult]

When you run the SDL 1.2x version of smooth (see #516) with a proper config file and proper bmp file (with the files in mapedit/tools/smooth run smooth -i rough.bmp -c smooth.conf -o smoothed_1.bmp -d 3) you will notice that the plugins don't finish their section work -> the output bitmap does not get written.

Tagging Artaxerxes but don't expect him to react on his decades old tool :) @AurelienMarchand

[AurelienMarchand]

I was not expecting to use this tool anymore! I would be surprised if it was at all related to SDL2. Will check