Leaving Password Expiration Warning field blank as directed causes arithmetic error

The directions on the configuration form say to "Leave [Password Expiration Warning] blank to not send or display any warnings."

However, the code of password_policy.module assumes on line 382 that the warning field is a comma-separated list of numbers and then proceeds on line 384 to attempt to multiply the maximum value. Leaving the field blank as directed results in the error message, "Warning: A non-numeric value encountered in password_policy_user_login()" each time a user logs in.

Entering a 0 in this field gets rid of the error message and does not appear to cause any ill effects. I would recommend causing the form to default to a 0 value instead of a null string, and changing line 382 of the module file to default to a 0 value if the value is "".

Thank you!