A parsing error that occurred on sqlite3 for "NOT NULL ORDER BY 1;" expression.

Fully reproducible code snippet

When I'm trying to parse the query below, a ParseError occurs:

import sqlglot
query = """SELECT a , b  FROM t1 WHERE b+a NOT NULL ORDER BY 1;"""
sqlglot.parse_one(query, read="sqlite")

error messages:

sqlglot.errors.ParseError: Invalid expression / Unexpected token. Line 1, Col: 40.
  SELECT a , b  FROM t1 WHERE b+a NOT NULL ORDER BY 1;

When I execute the following statement on sqlite3:

CREATE TABLE t1(a,b,c,d);
CREATE TABLE t2(e, f);
SELECT a , b  FROM t1 WHERE b+a NOT NULL ORDER BY 1;

It can be executed normally.