Segfault when decoding dash streams

[Thirumalaisamy K]

On MacOS 10.13.4, ffmpeg/ffplay build from latest git results in segfault 11 when reading the dash streams.

Sample Urls:

1. ​http://yt-dash-mse-test.commondatastorage.googleapis.com/media/feelings_vp9-20130806-manifest.mpd
2. ​http://yt-dash-mse-test.commondatastorage.googleapis.com/media/car-20120827-manifest.mpd

My build config is

--enable-static --disable-shared --disable-debug --disable-doc --enable-gpl --enable-version3 --enable-nonfree --enable-pthreads --enable-runtime-cpudetect --pkg-config-flags=--static --extra-version=9e2b4c7ecc --enable-libxml2 --enable-openssl --enable-sdl2 --enable-libvpx --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libx264 --enable-libx265 --enable-libaom --enable-libkvazaar --enable-libfdk-aac --enable-libopencore_amrwb --enable-libopencore_amrnb --enable-libvidstab

Reprodicibility: Always
Regression since the commit 9e2b4c7ecc3014310d01e918800f7f7f36596598
No issues with 0b3c1854cb9893a05564f25594a48947e9a163e9

[Thirumalaisamy K]

From Mac's backtrcae

Crashed Thread:        8  read_thread

Exception Type:        EXC_BAD_ACCESS (SIGSEGV)
Exception Codes:       KERN_INVALID_ADDRESS at 0x0000000000000010
Exception Note:        EXC_CORPSE_NOTIFY

Termination Signal:    Segmentation fault: 11
Termination Reason:    Namespace SIGNAL, Code 0xb
Terminating Process:   exc handler [0]

[Steven Liu]

fixed by commit : 93fc96e1997de1ca4e452ca923dfa0ee5a35e589