TUN-3107: UnregisterConnection shouldn't wrap nil error as RPC error

tunnelrpc/pogs/connectionrpc.go

@@ -229,5 +229,8 @@ func (c TunnelServer_PogsClient) Unregister(ctx context.Context) error {
 		return nil
 	})
 	_, err := promise.Struct()
+	if err != nil {
 		return wrapRPCError(err)
+	}
+	return nil
 }

tunnelrpc/pogs/errors.go

@@ -37,9 +37,12 @@ func (re *RPCError) Error() string {
 }
 
 func wrapRPCError(err error) *RPCError {
+	if err != nil {
 		return &RPCError{
 			err: err,
 		}
+	}
+	return nil
 }
 
 func newRPCError(format string, args ...interface{}) *RPCError {