revert r8428, the check was not that useless should fix constant pts=0 with broken demuxers
revert r8428, the check was not that useless
should fix constant pts=0 with broken demuxers


git-svn-id: a4d7c1866f8397a4106e0b57fc4fbf792bbdaaaf@8454 9553f0bf-9b14-0410-a0b8-cfaf0461ba5b

prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg,prajnashi/ffmpeg