Outerjoin searches

Unless we do this, any record not being referenced by all child
relations will get excluded from the search.

flask_admin/contrib/sqla/view.py

@@ -741,8 +741,8 @@ class ModelView(BaseModelView):
             # Apply search-related joins
             if self._search_joins:
                 for table in self._search_joins:
-                    query = query.join(table)
-                    count_query = count_query.join(table)
+                    query = query.outerjoin(table)
+                    count_query = count_query.outerjoin(table)
 
                     joins.add(table.name)