lavf/id3v2: fail read_apic on EOF reading mimetype

avio_read may return EOF, leaving the mimetype array unitialized. fail
early when this occurs to avoid using the array in an unitialized state.

Reviewed-by: Tomas Härdin <tjoppen@acc.umu.se>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>
(cherry picked from commit ee1e39a576)
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/id3v2.c

@@ -547,7 +547,7 @@ static void read_apic(AVFormatContext *s, AVIOContext *pb, int taglen,
                       int isv34)
 {
     int enc, pic_type;
-    char mimetype[64];
+    char mimetype[64] = {0};
     const CodecMime *mime     = ff_id3v2_mime_tags;
     enum AVCodecID id         = AV_CODEC_ID_NONE;
     ID3v2ExtraMetaAPIC *apic  = NULL;
@@ -569,7 +569,9 @@ static void read_apic(AVFormatContext *s, AVIOContext *pb, int taglen,
     if (isv34) {
         taglen -= avio_get_str(pb, taglen, mimetype, sizeof(mimetype));
     } else {
-        avio_read(pb, mimetype, 3);
+        if (avio_read(pb, mimetype, 3) < 0)
+            goto fail;
+
         mimetype[3] = 0;
         taglen    -= 3;
     }