tools/target_dem_fuzzer: ignore avformat_find_stream_info() failure

Such a failure should not be fatal and its worth testing this path too
Signed-off-by: Michael Niedermayer <michael@niedermayer.cc>

tools/target_dem_fuzzer.c

@@ -141,8 +141,6 @@ int LLVMFuzzerTestOneInput(const uint8_t *data, size_t size) {
     }
 
     ret = avformat_find_stream_info(avfmt, NULL);
-    if (ret < 0)
-        goto end;
 
     av_init_packet(&pkt);