remoting: Handle non-fatal errors in gst_parse_launch
gst_parse_launch can return non-NULL even though an error is set. This indicates "a recoverable parsing error and you can try to play the pipeline", however given that we don't (and likely can't) make any attempt to correct the situation, we should treat this as fatal and not try to carry on.
Signed-off-by: Ray Smith rsmith@brightsign.biz