[XAM] Fixed lack of UI notification for headless notifications.

- Fixes regression introduced in previous commit
- Fixed issue with multiple input if certain UI is active

src/xenia/kernel/xam/xam_input.cc

@@ -181,6 +181,10 @@ dword_result_t XamInputGetKeystrokeEx_entry(
 
   keystroke.Zero();
 
+  if (kernel_state()->xam_state()->xam_dialogs_shown_ > 0) {
+    return X_ERROR_SUCCESS;
+  }
+
   uint32_t user_index = *user_index_ptr;
   auto input_system = kernel_state()->emulator()->input_system();
   auto lock = input_system->lock();