Fix icons search problem
Fix icons search problem

The icons search algorithm was searching first under the
/usr/share/pixmaps directory for the icons which had as a
result to miss the 256x256 icon under /usr/share/icons/hicolor/256x256/apps/
and retrieve the 48x48 icon

Now the algorithm first searches the $XDG_DATA_DIRS
and then the fallback directory (/usr/share/pixmaps)

ukazap/youtube-dl-gui,MrS0m30n3/youtube-dl-gui,Sofronio/youtube-dl-gui,pr0d1r2/youtube-dl-gui,ukazap/youtube-dl-gui,dstftw/youtube-dl-gui,MrS0m30n3/youtube-dl-gui,Sofronio/youtube-dl-gui,pr0d1r2/youtube-dl-gui,dstftw/youtube-dl-gui