p2p/server.go: Attempt to print destDial while it is nil

[buonhobo]

I don't know why it does not regularly fail, but I've been trying to run quorum inside a Unikraft VM and this line makes the program crash. It tries to print destDial without checking if it is nil first.

I'm not an expert in go or blockchains, but adding check before printing this solved the issue for me.

https://github.com/Consensys/quorum/blob/8585ac91f198ad53977b5293a9dfdf366779b556/p2p/server.go#L996