HackStudio: Show the 'Save as...' dialog when saving uncreated file

Previously when user wanted to save an uncreated file, the program
would just quietly ignore the save request, without giving any message.
This can be seen when creating a new editor in split view mode.

Userland/DevTools/HackStudio/HackStudioWidget.cpp

@@ -601,7 +601,7 @@ NonnullRefPtr<GUI::Action> HackStudioWidget::create_save_action()
 {
     return GUI::CommonActions::make_save_action([&](auto&) {
         if (active_file().is_empty())
-            return;
+            m_save_as_action->activate();
 
         current_editor_wrapper().save();