Fix #147476: errors/crashes calling node menus outside the Node Editor

Calling node menus in the context of a different editor can lead to
errors in many places (e.g. checking on space_data tree_type/
node_tree_sub_type), so to resolve, add a very general poll function to
the NodeMenu class.

Pull Request: https://projects.blender.org/blender/blender/pulls/147512

scripts/startup/bl_ui/node_add_menu.py

@@ -115,6 +115,10 @@ class NodeMenu(Menu):
     root_asset_menu: str
     pathing_dict: dict[str, str]
 
+    @classmethod
+    def poll(cls, context):
+        return context.space_data.type == 'NODE_EDITOR'
+
     @classmethod
     def node_operator(cls, layout, node_type, *, label=None, poll=None, search_weight=0.0, translate=True):
         """The main operator defined for the node menu.