Not parsing SQL with "is not null"

[nmaguiar]

Description
When using af.fromSQL or af.fromSQL2NLinq if a SQL where statement has the condition "is not null" an parsing error is thrown

To Reproduce
Steps to reproduce the behavior:

1. Execute af.fromSQL or af.fromSQL2NLinq of "select * from TMP where a is not null"
2. See error

Expected behavior
It should not throw an error and just interpret the "is not null"

Additional context
n/a