Qt4: do not explode if MyDocument isn't available
Qt4: do not explode if MyDocument isn't available

See http://forum.videolan.org/viewtopic.php?f=14&t=78396

krichter722/vlc,shyamalschandra/vlc,vlc-mirror/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,shyamalschandra/vlc,vlc-mirror/vlc,jomanmuk/vlc-2.2,xkfz007/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc,krichter722/vlc,shyamalschandra/vlc,vlc-mirror/vlc,vlc-mirror/vlc,krichter722/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,vlc-mirror/vlc-2.1,shyamalschandra/vlc,jomanmuk/vlc-2.1,shyamalschandra/vlc,vlc-mirror/vlc-2.1,vlc-mirror/vlc,vlc-mirror/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,jomanmuk/vlc-2.1,xkfz007/vlc,xkfz007/vlc,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.1,jomanmuk/vlc-2.2,krichter722/vlc,krichter722/vlc,vlc-mirror/vlc-2.1,krichter722/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,vlc-mirror/vlc-2.1,xkfz007/vlc,xkfz007/vlc,jomanmuk/vlc-2.2,shyamalschandra/vlc,krichter722/vlc,vlc-mirror/vlc,vlc-mirror/vlc-2.1,shyamalschandra/vlc