Sanitize owner data in client (fixes ddnet#4388)

and don't access out of scope on owner < 0

Version 15.7

Escape skin name when downloading (fixes ddnet#4333)

Version 15.6.2

Support unicode filenames on windows with pnglite (fixes ddnet#4301)

Support unicode filenames on windows with pnglite (fixes ddnet#4301)

Version 15.6.1

Fix characters disappearing (fixes ddnet#4285)

Fix pickup network clipping

Version 15.5.4