The "without a refuge/protector" translation supposes anabhissaro to be an adjective formed from "na abhissarati", the passive form of the verb abhisarati, from the root *sar (the same root as sarana, refuge).
The "without a Supreme God" translation, since it posits a connection between anabhissaro and issaro (God) would need to be formed from an entirely different root: *is or *iis. But since there is no such verb as abhissati or abhiissati, one would first need to form the noun issaro, then prefix it with abhi-, then add the negative an-.
Both ways are possible, but the second is extremely improbable, for had the word been formed in this way we should expect to meet with instances of the unnegated form 'abhissaro' in the sense of "Supreme God". But there is no such instantiation even in the commentaries, let alone the Suttas.