fixes "undefined method `id' for nil:NilClass: searching model "dmsf_files""

seems sometimes dmsf_file.project is nil
Merge pull request #219 from williamschey/master

Hey hey
New devel branch 1.4.8
#205 Ampersands in filenames
#212 Incorrect revision information in email notification
#214 Required DMSF custom field prevents documents to be saved
Merge branch 'devel-1.4.8' of https://github.com/danmunn/redmine_dmsf into devel-1.4.8