issue #101: fix for NPE at MediaPlayer.stopAndPrepareFilename
issue #91: added blank frame rendering at media playback close
issue #91: removed unnecessary state checks to BaseMediaPlayer.stop()
Revert "issue #91: removed unnecessary state checks to BaseMediaPlayer.stop()"

This reverts commit 7db95b97e20a5a631ac02176218ccc2d37977f50.