Handle 500 response better when generating PDF

[Cooryd]

We've not yet hooked up the staging PDF service to call off to Exeter so clicking the generate button in client produces a 500 response. I would expect this to be handled by the client in the same way a failed response is, a red popup informing the user something went wrong. Instead we get a console error and the application goes into a broken state (ie: auto save no longer works)

The above error occurred in task wr
    created by takeLatest(EXPORT_PDF, wr)
    created by Ir
    created by ri
Tasks cancelled due to error:
takeLatest(EXPORT_PDF, wr)
takeLatest(SET_FOCUS, xr)
takeLatest(SET_ACTIVE_EXPORT_PDF_TASK, Nr)
takeLatest(CANCEL_EXPORT_PDF_TASK, Sr)
ei
Dr
mr
en
Jr

[GrazingScientist]

I can reproduce this. Also, after clicking the PDF button, the article segment navigation on the left does not react anymore.