From f34e738ddd6230d434b3cb709ccdce4499437882 Mon Sep 17 00:00:00 2001
From: Dave Pearson <davep@davep.org>
Date: Mon, 8 May 2023 09:16:58 +0100
Subject: [PATCH] Ensure the cursor node is set to None when the tree goes
 empty

Up until now there wasn't really a way for the tree to go empty, outside of
clear/reset. Now that we can remove nodes on the fly, that is possible. This
takes that into account.

See #2462.
---
 src/textual/widgets/_tree.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/textual/widgets/_tree.py b/src/textual/widgets/_tree.py
index 27bb2487f..1d399fd52 100644
--- a/src/textual/widgets/_tree.py
+++ b/src/textual/widgets/_tree.py
@@ -845,6 +845,8 @@ class Tree(Generic[TreeDataType], ScrollView, can_focus=True):
             self._cursor_node = node
             if previous_node != node:
                 self.post_message(self.NodeHighlighted(node))
+        else:
+            self._cursor_node = None
 
     def watch_guide_depth(self, guide_depth: int) -> None:
         self._invalidate()