Fix the `wt` action in defterm windows (#11646)

This is a pretty obvious typo in retrospect. Never hit it before, because in all non-defterm windows, the `_startupActions` always has one action. 

* [x] Closes #11463

src/cascadia/TerminalApp/AppActionHandlers.cpp

@@ -556,7 +556,7 @@ namespace winrt::TerminalApp::implementation
             auto actions = winrt::single_threaded_vector<ActionAndArgs>(std::move(
                 TerminalPage::ConvertExecuteCommandlineToActions(realArgs)));
 
-            if (_startupActions.Size() != 0)
+            if (actions.Size() != 0)
             {
                 actionArgs.Handled(true);
                 ProcessStartupActions(actions, false);