fixed: failure when submitting a dataform that sends mail with an empty file field

docs/changelog/7.x.x.txt

@@ -3,6 +3,7 @@
    unmodified has been moved to the configuration file under the
    "exportBianryExtensions" field.
  - fixed: some default assets have ids shorter than 22 characters
+ - fixed: failure when submitting a dataform that sends mail with an empty file field
 
 7.6.0
  - added: users may now customize the post received page for the CS

lib/WebGUI/Asset/Wobject/DataForm.pm

@@ -485,7 +485,9 @@ sub getAttachedFiles {
         my $form = $self->_createForm($field, $entryData->{$field->{name}});
         if ($form->can('getStorageLocation')) {
             my $storage = $form->getStorageLocation;
-            push @paths, $storage->getPath($storage->getFiles->[0]);
+            if ($storage) {
+                push @paths, $storage->getPath($storage->getFiles->[0]);
+            }
         }
     }
     return \@paths;