Fix sorting info bug when Buefy grid doesn't support it

tailbone/templates/grids/buefy.mako

@@ -165,12 +165,15 @@
           return {
               data: ${json.dumps(grid_data['data'])|n},
               loading: false,
-              sortField: '${grid.sortkey}',
-              sortOrder: '${grid.sortdir}',
               rowStatusMap: ${json.dumps(grid_data['row_status_map'])|n},
               ## TODO: should be dumping json from server here
               checkedRows: [],
 
+              % if grid.sortable:
+              sortField: '${grid.sortkey}',
+              sortOrder: '${grid.sortdir}',
+              % endif
+
               % if grid.pageable:
               % if static_data:
               total: ${len(grid_data['data'])},