avformat/qcp: Check for read failure in header

Fixes: Use of uninitialized value
Fixes: 71551/clusterfuzz-testcase-minimized-ffmpeg_dem_QCP_fuzzer-4647386712965120

Found-by: continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit f52b9d0583)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/qcp.c

@@ -105,7 +105,8 @@ static int qcp_read_header(AVFormatContext *s)
 
     st->codecpar->codec_type = AVMEDIA_TYPE_AUDIO;
     st->codecpar->ch_layout  = (AVChannelLayout)AV_CHANNEL_LAYOUT_MONO;
-    avio_read(pb, buf, 16);
+    if (avio_read(pb, buf, 16) != 16)
+        return AVERROR_INVALIDDATA;
     if (is_qcelp_13k_guid(buf)) {
         st->codecpar->codec_id = AV_CODEC_ID_QCELP;
     } else if (!memcmp(buf, guid_evrc, 16)) {