Negate code as per node docs

lib/browser/rpc-server.js

@@ -142,7 +142,7 @@ const exceptionToMeta = function (error) {
 const throwRPCError = function (message) {
   const error = new Error(message)
   error.code = 'EBADRPC'
-  error.errno = 72
+  error.errno = -72
   throw error
 }