I have a Safariland ALS holster for my Sig 226 with a surefire X300u on it. That holster does not need the light on the gun for it to lock securely.
I run a similar holster with my M&P...light, no light...different lights (X300, X300u, inforce APL), all work just fine.
I would be surprised if it didnt work with your rail mounted laser.