Fix issue where ListView appeared detached from Screen

src/textual/dom.py

@@ -259,7 +259,7 @@ class DOMNode(MessagePump):
         from .screen import Screen
 
         node = self
-        while node and not isinstance(node, Screen):
+        while node is not None and not isinstance(node, Screen):
             node = node._parent
         if not isinstance(node, Screen):
             raise NoScreen("node has no screen")

src/textual/widgets/_list_view.py

@@ -85,7 +85,7 @@ class ListView(Vertical, can_focus=True, can_focus_children=False):
 
     async def clear(self) -> None:
         """Clear all items from the ListView."""
-
+        await self.query("ListView > ListItem").remove()
         await self.emit(self.ChildrenUpdated(self, self.children))
 
     def action_select(self) -> None: