Fix Python error when trying to call the Search Menu with no object

When pressing F3 to bring up the Search Menu, an error appeared
because the MoveModifierToNodes operator's poll method did not
consider the context where no object was selected.

Pull Request: https://projects.blender.org/blender/blender/pulls/107310

scripts/startup/bl_operators/geometry_nodes.py

@@ -43,6 +43,8 @@ def get_context_modifier(context):
     if context.area.type == 'PROPERTIES':
         modifier = context.modifier
     else:
+        if context.object is None:
+            return False
         modifier = context.object.modifiers.active
     if modifier is None or modifier.type != 'NODES':
         return None