avcodec/mpeg4videodec: Remove use of FF_PROFILE_MPEG4_SIMPLE_STUDIO as indicator of studio profile

The profile field is changed by code inside and outside the decoder,
its not a reliable indicator of the internal codec state.
Maintaining it consistency with studio_profile is messy.
Its easier to just avoid it and use only studio_profile

Fixes: assertion failure
Fixes: ffmpeg_crash_9.avi

Found-by: Thuan Pham, Marcel Böhme, Andrew Santosa and Alexandru Razvan Caciulescu with AFLSmart
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavcodec/error_resilience.c

@@ -814,8 +814,7 @@ static int er_supported(ERContext *s)
 {
     if(s->avctx->hwaccel && s->avctx->hwaccel->decode_slice           ||
        !s->cur_pic.f                                                  ||
-       s->cur_pic.field_picture                                       ||
-       s->avctx->profile == FF_PROFILE_MPEG4_SIMPLE_STUDIO
+       s->cur_pic.field_picture
     )
         return 0;
     return 1;

libavcodec/h263dec.c

@@ -47,9 +47,10 @@
 
 static enum AVPixelFormat h263_get_format(AVCodecContext *avctx)
 {
+    MpegEncContext *s = avctx->priv_data;
     /* MPEG-4 Studio Profile only, not supported by hardware */
     if (avctx->bits_per_raw_sample > 8) {
-        av_assert1(avctx->profile == FF_PROFILE_MPEG4_SIMPLE_STUDIO);
+        av_assert1(s->studio_profile);
         return avctx->pix_fmt;
     }
 
@@ -670,7 +671,8 @@ retry:
 
     av_assert1(s->bitstream_buffer_size == 0);
 frame_end:
-    ff_er_frame_end(&s->er);
+    if (!s->studio_profile)
+        ff_er_frame_end(&s->er);
 
     if (avctx->hwaccel) {
         ret = avctx->hwaccel->end_frame(avctx);

libavcodec/mpeg4videodec.c

@@ -3244,7 +3244,6 @@ end:
     s->avctx->has_b_frames = !s->low_delay;
 
     if (s->studio_profile) {
-        av_assert0(s->avctx->profile == FF_PROFILE_MPEG4_SIMPLE_STUDIO);
         if (!s->avctx->bits_per_raw_sample) {
             av_log(s->avctx, AV_LOG_ERROR, "Missing VOL header\n");
             return AVERROR_INVALIDDATA;