This let the application get an error message when ndisrc emits an EOS triggered by 'connect-timeout' for instance. Without this, a simple gst-launch-1.0 ndisrc pad-name="badname" connect-timeout=1000 ! ndisrcdemux ! fakesink will block.
The NdiSrcMeta is no longer needed after the demux and if kept, it generates many errors as the transform_func() always false.
This simplifies the code considerably.