MediaPlayer: Fix early main exit race-condition at startup.

MediaPlayer.java: Quit early if no file is specified.
MediaPlayer.java: Quit early if file is not found.
run.sh: Use jogl-all-mobile.jar instead of jogl-all.jar to skip desktop GL enumeration startup delay.

Signed-off-by: Xerxes Rånby <xerxes@gudinna.com>