Commit 4505c22689 for ffmpeg

commit 4505c22689e5865cb5f76830ffc01266317b3894
Author: Michael Niedermayer <michael@niedermayer.cc>
Date:   Tue Oct 6 07:08:54 2026 +0200

    avformat/dashdec: Check that the referenced representation has an id

    Fixes: NULL pointer dereference
    Fixes: pBjbWIWDyAJK
    NULL pointer dereference Replicated through UnModified FFmpeg (ffprobe) with UBSAN
    Regression since: e7696357de
    Found during triage of the security report XmvwOQImSoeX

diff --git a/libavformat/dashdec.c b/libavformat/dashdec.c
index ef33ff5ff3..0911bd73fa 100644
--- a/libavformat/dashdec.c
+++ b/libavformat/dashdec.c
@@ -2296,7 +2296,7 @@ static int dash_read_header(AVFormatContext *s)
             if (!ref->nb_assoc_stream)
                 continue;
             const AVDictionaryEntry *id = av_dict_get(ref->assoc_stream[0]->metadata, "id", NULL, AV_DICT_MATCH_CASE);
-            if (!strcmp(rep->dependencyid, id->value))
+            if (id && !strcmp(rep->dependencyid, id->value))
                 break;
         }
         if (j >= c->n_videos || !av_strstart(rep->codecs, "lvc1", NULL) ||