In 4.3 PTR it appears dividing by 0 is no longer working

so

local inf = 1/0

or

local serNaN = tostring(0/0)

or other similar number or hacks. A lot of mods are using these and they are not functional on PTR.

Intended change, or just a bug, don't know yet. Have to wait and see what blizzard says about this.