tracker-extract: Fix build with libav when libmediaaart is disabled
tracker-extract: Fix build with libav when libmediaaart is disabled

https://bugzilla.gnome.org/show_bug.cgi?id=728370

hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker,outofbits/tracker,outofbits/tracker,hoheinzollern/tracker