Fix template rendering in firefox and internet explorer with Web UI

• Using a 9.1-SNAPSHOT (04/04)
• Using firefox 52 or IE11 or Edge (cannot be reproduced in chrome / chromium)

STEPS TO REPRODUCE

• Install template rendering samples
• Open a project document (e.g. http://localhost:8080/nuxeo/ui/#!/browse/default-domain/workspaces/templatesamples/recruiting )
• Try to render a template

BUG ENCOUNTERED

• An error message is shown:

  Unable to render document 'response did not carry a valid blob'

EXPECTED

• No error message and rendition is downloaded