Does whiskey go bad by freezing?
Putting strong spirits in the freezer should not harm them. The solubility of air gases increases at low temperature, which is why you see bubbles as it warms up.

Drinks with a lower alcohol content will be affected in the freezer. There is potential to freeze water out of anything with an alcohol content of 28% or lower. Many people use the freezer to increase the alcohol content of their home brew in UK, by freezing water out of it - the alcohol stays in the liquid portion.