PG doesn't freeze until about -8 F (-22 C), and VG's freeze point is -36 F (-37.78 C). Unless you have a commercial/industrial/scientific freezer I doubt you are going to reach this.
So no; removing and replacing your nic in a household/residential freezer isn't going to harm it. Though I have seen a "standard practice," commonly mentioned, recommending allowing the nic to come to room temp before using. No explanation; so I don't know if this is simply for convenience (warmer = thinner viscosity = easier to work with) or if there is some chemical benefit.