bit: replace assert() by proper check.

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavformat/bit.c

@@ -72,7 +72,8 @@ static int read_packet(AVFormatContext *s,
 
     sync = get_le16(pb); // sync word
     packet_size = get_le16(pb) / 8;
-    assert(packet_size < 8 * MAX_FRAME_SIZE);
+    if(packet_size > MAX_FRAME_SIZE)
+        return AVERROR(EIO);
 
     ret = get_buffer(pb, (uint8_t*)buf, (8 * packet_size) * sizeof(uint16_t));
     if(ret<0)