add exception

src/app/browser/main/tab.cpp

@@ -120,15 +120,16 @@ void Tab::update(
         PAGE_NUMBER
     );
 
-    if (pageWidget != nullptr)
+    if (pageWidget == nullptr)
     {
+        throw _("Tab page not found!");
+    }
+
     pageWidget->activate_action(
         "page.update"
     );
 }
 
-} // @TODO
-
 // Private helpers
 tab::Label * Tab::get_tabLabel(
     const int & PAGE_NUMBER