[FIX] discuss: error breadcrumb

Before this commit
When discuss is the final state, the system will not change the browser url.

After this commit:
Browser url will be correct when using breadcrumb

closes odoo/odoo#92477

Signed-off-by: Sébastien Theys (seb) <seb@odoo.com>

addons/mail/static/src/widgets/discuss/discuss.js

@@ -147,6 +147,7 @@ const DiscussWidget = AbstractAction.extend({
             'o-update-control-panel',
             this._updateControlPanelEventListener
         );
+        this._lastPushStateActiveThread = null;
     },
 
     //--------------------------------------------------------------------------