Set revision context before clearing the screen

This prevents the clear method (which set the current record to null) to update
the URL with the old revision and thus opens a new tab.

Closes #14577
(grafted from 804f498790430d3fd89a274d5e261fb80b0c5520)

--HG--
branch : 7.0

sao/src/tab.js

@@ -986,10 +986,12 @@
                         revision = revisions[revisions.length - 1][0];
                     }
                     if (revision != this.screen.context._datetime) {
-                        this.screen.clear();
                         // Update group context that will be propagated by
                         // recreating new group
                         this.screen.group._context._datetime = revision;
+                        // clear after updating the datetime such that the tab
+                        // compute already the right URL
+                        this.screen.clear();
                         if (this.screen.current_view.view_type != 'form') {
                             this.screen.search_filter(
                                     this.screen.screen_container

tryton/tryton/gui/window/form.py

@@ -324,9 +324,9 @@ class Form(TabContent):
                 and revision < revisions[-1][0]):
             revision = revisions[-1][0]
         if revision != self.screen.context.get('_datetime'):
-            self.screen.clear()
             # Update root group context that will be propagated
             self.screen.group._context['_datetime'] = revision
+            self.screen.clear()
             if self.screen.current_view.view_type != 'form':
                 self.screen.search_filter(
                     self.screen.screen_container.get_text())