Customize the empty formset message for the document type metadata type relationship view.

Signed-off-by: Michael Price <loneviking72@gmail.com>

mayan/apps/metadata/views.py

@@ -592,6 +592,9 @@ class SetupDocumentTypeMetadataTypes(FormView):
     def get_extra_context(self):
         return {
             'form_display_mode_table': True,
+            'form_empty_label': _(
+                'No metadata types available. Add at least one.'
+            ),
             'object': self.get_object(),
             'title': _(
                 'Metadata types for document type: %s'