Fix: improve poll for NodePanelOperator

Also check for actually being in the Node Editor, otherwise we get
errors from other editors (e.g. on F3 search) due to missing
'edit_tree'.

Pull Request: https://projects.blender.org/blender/blender/pulls/109125

scripts/startup/bl_operators/node.py

@@ -250,13 +250,10 @@ class NODE_OT_tree_path_parent(Operator):
 class NodePanelOperator():
     @classmethod
     def poll(cls, context):
-        snode = context.space_data
-        if snode is None:
+        space = context.space_data
+        if not space or space.type != 'NODE_EDITOR' or not space.edit_tree:
             return False
-        tree = snode.edit_tree
-        if tree is None:
-            return False
-        if tree.is_embedded_data:
+        if space.edit_tree.is_embedded_data:
             return False
         return True