[FIX] web: correctly update this.widgets

Old subwidgets of a widget inhereriting from BasicRender were not
correctly destroyed. This was the cause of various problems when
cycling over this.widgets.

addons/web/static/src/js/views/basic/basic_renderer.js

@@ -510,12 +510,15 @@ var BasicRenderer = AbstractRenderer.extend({
         var oldAllFieldWidgets = this.allFieldWidgets;
         this.allFieldWidgets = {}; // TODO maybe merging allFieldWidgets and allModifiersData into "nodesData" in some way could be great
         this.allModifiersData = [];
+        var oldWidgets = this.widgets;
+        this.widgets = [];
         return this._renderView().then(function () {
             _.each(oldAllFieldWidgets, function (recordWidgets) {
                 _.each(recordWidgets, function (widget) {
                     widget.destroy();
                 });
             });
+            _.invoke(oldWidgets, 'destroy');
         });
     },
     /**

addons/web/static/src/js/views/kanban/kanban_renderer.js

@@ -396,8 +396,6 @@ var KanbanRenderer = BasicRenderer.extend({
      */
     _renderView: function () {
         var self = this;
-        var oldWidgets = this.widgets;
-        this.widgets = [];
 
         // render the kanban view
         var isGrouped = !!this.state.groupedBy.length;
@@ -418,7 +416,6 @@ var KanbanRenderer = BasicRenderer.extend({
                 self.$el.toggleClass('o_kanban_ungrouped', !isGrouped);
                 self.$el.append(fragment);
                 self._toggleNoContentHelper();
-                _.invoke(oldWidgets, 'destroy');
                 if (self._isInDom) {
                     _.invoke(self.widgets, 'on_attach_callback');
                 }