avfilter/lavfutils: call av_find_stream_info() before reading various information about the stream

No testcase with unmodified source is known
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>

libavfilter/lavfutils.c

@@ -44,6 +44,11 @@ int ff_load_image(uint8_t *data[4], int linesize[4],
         return ret;
     }
 
+    if ((ret = avformat_find_stream_info(format_ctx, NULL)) < 0) {
+        av_log(log_ctx, AV_LOG_ERROR, "Find stream info failed\n");
+        return ret;
+    }
+
     codec_ctx = format_ctx->streams[0]->codec;
     codec = avcodec_find_decoder(codec_ctx->codec_id);
     if (!codec) {