lua/playlist/koreus: lack of UTF-8 conversion leads to assert

If VLC is compiled with debug enabled, using the koreus.lua playlist script trying to open the following URL

http://www.koreus.com/video/migrants-applaudis-croisilles.html

VLC aborts due to an assertion failure:

Assertion failed: (psz_val == NULL || IsUTF8( psz_val )), function vlc_meta_Set, file ../../extras/package/macosx/../../../src/input/meta.c, line 127.

Attached is the full crashlog