[FIX] web(_*): views: render action buttons in dialogs

Commit 516b1a6c72 fixes a bug with action buttons not being displayed when they
should in dialogs. However, it makes the assumption that either $node or
this.options.$buttons exist, which is not always the case (e.g. dashboard).

This rev. moves that logic out of the views to the view_manager, and protects
the call of empty() on this.options.$buttons.

addons/web/static/src/js/view_manager.js

@@ -293,15 +293,16 @@ var ViewManager = Widget.extend(ControlPanelMixin, {
     render_view_control_elements: function() {
         if (!this.active_view.control_elements) {
             var view_controller = this.active_view.controller;
+            var $buttons = this.flags.$buttons;
             var elements = {};
             if (!this.flags.headless) {
                 elements = {
-                    $buttons: !this.flags.footer_to_buttons ? $("<div>") : undefined,
+                    $buttons: $("<div>"),
                     $sidebar: $("<div>"),
                     $pager: $("<div>"),
                 };
             }
-            view_controller.render_buttons(elements.$buttons);
+            view_controller.render_buttons($buttons ? $buttons.empty() : elements.$buttons);
             view_controller.render_sidebar(elements.$sidebar);
             view_controller.render_pager(elements.$pager);
             // Remove the unnecessary outer div

addons/web/static/src/js/views/form_view.js

@@ -190,7 +190,6 @@ var FormView = View.extend(common.FieldManagerMixin, {
         this.$buttons.on('click', '.oe_form_button_cancel',
                          this.guard_active(this.on_button_cancel));
 
-        $node = $node || this.options.$buttons.empty();
         if ($node) {
             this.$buttons.appendTo($node);
         } else {

addons/web/static/src/js/views/list_view.js

@@ -282,7 +282,6 @@ var ListView = View.extend( /** @lends instance.web.ListView# */ {
 
             this.$buttons.find('.o_list_button_add').click(this.proxy('do_add_record'));
 
-            $node = $node || this.options.$buttons;
             if ($node) {
                 this.$buttons.appendTo($node);
             } else {

addons/web_calendar/static/src/js/web_calendar.js

@@ -259,7 +259,6 @@ var CalendarView = View.extend({
 
         this.$buttons.find('.o_calendar_button_' + this.mode).addClass('active');
         
-        $node = $node || this.options.$buttons;
         if ($node) {
             this.$buttons.appendTo($node);
         } else {

addons/web_diagram/static/src/js/diagram.js

@@ -361,7 +361,6 @@ var DiagramView = View.extend({
             self.add_node();
         });
 
-        $node = $node || this.options.$buttons;
         this.$buttons.appendTo($node);
     },
 

addons/web_kanban/static/src/js/kanban_view.js

@@ -312,7 +312,6 @@ var KanbanView = View.extend({
         this.$buttons = $(QWeb.render("KanbanView.buttons", {'widget': this, display: display}));
         this.$buttons.on('click', 'button.o-kanban-button-new', this.add_record.bind(this));
 
-        $node = $node || this.options.$buttons;
         this.$buttons.appendTo($node);
     },