Update ParseUser.js

Author: dblythy

src/ParseUser.js

@@ -425,7 +425,10 @@ class ParseUser extends ParseObject {
     if (options.hasOwnProperty('installationId')) {
       signupOptions.installationId = options.installationId;
     }
-    if (options.hasOwnProperty('context') && typeof options.context === 'object') {
+    if (
+      options.hasOwnProperty('context') &&
+      Object.prototype.toString.call(options.context) === '[object Object]'
+    ) {
       signupOptions.context = options.context;
     }