fix segmentation fault

src/textual/app.py

@@ -1071,7 +1071,7 @@ class App(Generic[ReturnType], DOMNode):
     async def shutdown(self):
         await self._disconnect_devtools()
         driver = self._driver
-        assert driver is not None
+        if driver is not None:
             driver.disable_input()
         await self.close_messages()
 

src/textual/widget.py

@@ -37,7 +37,6 @@ from .geometry import Offset, Region, Size, Spacing, clamp
 from .layouts.vertical import VerticalLayout
 from .message import Message
 from .reactive import Reactive, watch
-from .renderables.align import Align
 
 
 if TYPE_CHECKING:

tests/test_screens.py

@@ -77,3 +77,5 @@ async def test_screens():
     # Check we can't pop last screen
     with pytest.raises(ScreenStackError):
         app.pop_screen()
+
+    await app.shutdown()