Fix jsx-sort-prop-types issue with custom propTypes

Author: alitaheri

lib/rules/jsx-sort-prop-types.js

@@ -40,7 +40,7 @@ module.exports = function(context) {
   }
 
   function getValueName(node) {
-    return node.value.property.name;
+    return node.value.property && node.value.property.name;
   }
 
   function isCallbackPropName(propName) {

tests/lib/rules/jsx-sort-prop-types.js

@@ -276,6 +276,21 @@ ruleTester.run('jsx-sort-prop-types', rule, {
       requiredFirst: true
     }],
     parserOptions: parserOptions
+  }, {
+    code: [
+      'class First extends React.Component {',
+      '  render() {',
+      '    return <div />;',
+      '  }',
+      '}',
+      'First.propTypes = {',
+      '    fooRequired: MyPropType,',
+      '};'
+    ].join('\n'),
+    options: [{
+      requiredFirst: true
+    }],
+    parserOptions: parserOptions
   }, {
     code: [
       'class First extends React.Component {',