fix: replace default nulls in SSL options with undefineds

Related: #654

See also: nodejs/node@35274cb

Author: calzoneman

lib/socket.js

@@ -86,12 +86,12 @@ function Socket (uri, opts) {
   }
 
   // SSL options for Node.js client
-  this.pfx = opts.pfx || null;
-  this.key = opts.key || null;
-  this.passphrase = opts.passphrase || null;
-  this.cert = opts.cert || null;
-  this.ca = opts.ca || null;
-  this.ciphers = opts.ciphers || null;
+  this.pfx = opts.pfx || undefined;
+  this.key = opts.key || undefined;
+  this.passphrase = opts.passphrase || undefined;
+  this.cert = opts.cert || undefined;
+  this.ca = opts.ca || undefined;
+  this.ciphers = opts.ciphers || undefined;
   this.rejectUnauthorized = opts.rejectUnauthorized === undefined ? true : opts.rejectUnauthorized;
   this.forceNode = !!opts.forceNode;