[10.0] [FIX] [web_timeline] Correct write when grouped by (OCA#678)

* [FIX] Correct write when grouped by

* Remove blank lines

* Minor changes

web_timeline/static/src/js/web_timeline.js

@@ -36,6 +36,7 @@ odoo.define('web_timeline.TimelineView', function (require) {
 
         init: function (parent, dataset, view_id, options) {
             this.permissions = {};
+            this.grouped_by = false;
             return this._super.apply(this, arguments);
         },
 
@@ -283,6 +284,7 @@ odoo.define('web_timeline.TimelineView', function (require) {
             var self = this;
             var data = [];
             var groups = [];
+            this.grouped_by = group_bys;
             _.each(events, function(event) {
                 if (event[self.date_start]){
                     data.push(self.event_data_transform(event));
@@ -404,7 +406,9 @@ odoo.define('web_timeline.TimelineView', function (require) {
                 time.auto_date_to_str(start, self.fields[self.fields_view.arch.attrs.date_start].type);
             data[self.fields_view.arch.attrs.date_stop] =
                  time.auto_date_to_str(end, self.fields[self.fields_view.arch.attrs.date_stop].type);
-            data[self.fields_view.arch.attrs.default_group_by] = group;
+            if (self.grouped_by){
+                data[self.grouped_by[0]] = group;
+            }
             var id = item.evt.id;
             this.dataset.write(id, data);
         },