fix: #1600

https://github.com/flask-admin/flask-admin/issues/1600

flask_admin/contrib/sqla/form.py

@@ -154,7 +154,9 @@ class AdminModelConverter(ModelConverterBase):
             if len(prop.columns) > 1:
                 columns = filter_foreign_columns(model.__table__, prop.columns)
 
-                if len(columns) > 1:
+                if len(columns) == 0:
+                    return None
+                elif len(columns) > 1:
                     warnings.warn('Can not convert multiple-column properties (%s.%s)' % (model, prop.key))
                     return None
 

flask_admin/contrib/sqla/view.py

@@ -420,7 +420,9 @@ class ModelView(BaseModelView):
                 if len(p.columns) > 1:
                     filtered = tools.filter_foreign_columns(self.model.__table__, p.columns)
 
-                    if len(filtered) > 1:
+                    if len(filtered) == 0:
+                        continue
+                    elif len(filtered) > 1:
                         warnings.warn('Can not convert multiple-column properties (%s.%s)' % (self.model, p.key))
                         continue