Make sure we don't go into error state if error response has already been sent.
Make sure we don't go into error state if error response has already been sent.

jacwright/substance,abhaga/substance,andene/substance,michael/substance-1,substance/substance,podviaznikov/substance,andene/substance,michael/substance-1,stencila/substance,substance/substance,abhaga/substance,TypesetIO/substance,jacwright/substance,TypesetIO/substance,podviaznikov/substance