Two wallets with the same address
Creation of an address is an entirely offline operation; there is no communication with the network.
If you'd (with unfathomable luck) create the same address as someone else, then you'll see incoming payments to it appear in your wallet, and be able to spend them.
There is no provision for dealing with this, because there does not need to be any. The probability of this ever occurring is so mind-blowingly small that it is simply not a consideration.
For typical addresses, there exist 1461501637330902918203684832716283019655932542976 valid distinct ones.