segfault fix

Originally committed as revision 2764 to svn://svn.ffmpeg.org/ffmpeg/trunk

libavcodec/indeo3.c

@@ -1056,6 +1056,12 @@ static int indeo3_decode_frame(AVCodecContext *avctx,
     unsigned char *src, *dest;
     int y;
 
+    /* no supplementary picture */
+    if (buf_size == 0) {
+        *data_size = 0;
+        return 0;
+    }
+
     iv_decode_frame(s, buf, buf_size);
 
     if(s->frame.data[0])