rpza: return a meaningful error code.

libavcodec/rpza.c

@@ -250,15 +250,16 @@ static int rpza_decode_frame(AVCodecContext *avctx,
     const uint8_t *buf = avpkt->data;
     int buf_size = avpkt->size;
     RpzaContext *s = avctx->priv_data;
+    int ret;
 
     s->buf = buf;
     s->size = buf_size;
 
     s->frame.reference = 1;
     s->frame.buffer_hints = FF_BUFFER_HINTS_VALID | FF_BUFFER_HINTS_PRESERVE | FF_BUFFER_HINTS_REUSABLE;
-    if (avctx->reget_buffer(avctx, &s->frame)) {
+    if ((ret = avctx->reget_buffer(avctx, &s->frame)) < 0) {
         av_log(avctx, AV_LOG_ERROR, "reget_buffer() failed\n");
-        return -1;
+        return ret;
     }
 
     rpza_decode_stream(s);