The previous implementation crashed if run on a `builtin.module` using an `op_name` filter (because the initial value of `parent` in the while loop was a `nullptr`). This PR fixes the crash and adds a test.
The previous implementation crashed if run on a `builtin.module` using an `op_name` filter (because the initial value of `parent` in the while loop was a `nullptr`). This PR fixes the crash and adds a test.