OR-818 add redirect to 404 page when file is not found
OR-818 clean file uploads if page is left before message is created
Merge pull request #652 in OR/rse from OR/rse-gcrosmarie:OR-818 to master

* commit 'f09e9715dd86e303cd529ac257816ea71386737f':
  OR-818 clean file uploads if page is left before message is created
  OR-818 add redirect to 404 page when file is not found