No do not leave it blank it is required to e-file your Alabama State tax return. The only other alternative would be to print and mail your return.
See the following:
The following is from the Alabama Association of CPAs: http://www.ascpa.org/content/HomeNewsArticles/State-Issued-Driver-s-License-Required-When-Filing-201...
Quote: "In a continual effort to fight stolen identity tax refund fraud the
Alabama Department of Revenue is requiring taxpayers provide their state
issued driver's license (or state issued non-drivers ID) when
electronically filing their 2015 income tax return.
Tax preparers should make a good faith effort to obtain the actual
drivers' license or state issued non-drivers' id from their clients. In
the event that your client is a child or elderly person without a
driver's license or state issued non-drivers id you may enter the
following information in order to electronically file the tax return for
your client:
Driver's License #: 7777777
Driver's License State: AL
Issue Date: 11/1/11
Expiration date: 11/1/17