Throw only if the constructor key has a child named prototype

Author: delvedor

index.js

@@ -76,7 +76,9 @@ function scan (obj, { protoAction = 'error', constructorAction = 'error' } = {})
         delete node.__proto__ // eslint-disable-line no-proto
       }
 
-      if (constructorAction !== 'ignore' && Object.prototype.hasOwnProperty.call(node, 'constructor')) { // Avoid calling node.hasOwnProperty directly
+      if (constructorAction !== 'ignore' &&
+          Object.prototype.hasOwnProperty.call(node, 'constructor') &&
+          Object.prototype.hasOwnProperty.call(node.constructor, 'prototype')) { // Avoid calling node.hasOwnProperty directly
         if (constructorAction === 'error') {
           throw new SyntaxError('Object contains forbidden prototype property')
         }