avformat/mov: Free temp buffer upon negative sample_size error.

2d8d554f added a new error condition
to mov_read_stsz() but forgot to free a temporary buffer when it
occurs.
Signed-off-by: Dale Curtis <dalecurtis@chromium.org>
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

libavformat/mov.c

@@ -2886,6 +2886,7 @@ static int mov_read_stsz(MOVContext *c, AVIOContext *pb, MOVAtom atom)
     for (i = 0; i < entries && !pb->eof_reached; i++) {
         sc->sample_sizes[i] = get_bits_long(&gb, field_size);
         if (sc->sample_sizes[i] < 0) {
+            av_free(buf);
             av_log(c->fc, AV_LOG_ERROR, "Invalid sample size %d\n", sc->sample_sizes[i]);
             return AVERROR_INVALIDDATA;
         }