[Fix] forbid-prop-types: propWrapperFunctions breaks on identifiers.

Author: ljharb

lib/rules/forbid-prop-types.js

@@ -74,7 +74,7 @@ module.exports = {
      * @returns {void}
      */
     function checkForbidden(declarations) {
-      declarations.forEach(declaration => {
+      (declarations || []).forEach(declaration => {
         if (declaration.type !== 'Property') {
           return;
         }

tests/lib/rules/forbid-prop-types.js

@@ -398,6 +398,18 @@ ruleTester.run('forbid-prop-types', rule, {
     settings: {
       propWrapperFunctions: ['forbidExtraProps']
     }
+  }, {
+    code: [
+      'import { forbidExtraProps } from "airbnb-prop-types";',
+      'export const propTypes = {a: PropTypes.any};',
+      'export default function Component() {}',
+      'Component.propTypes = forbidExtraProps(propTypes);',
+    ].join('\n'),
+    // errors: [{message: ANY_ERROR_MESSAGE}], // TODO: make this pass
+    errors: [],
+    settings: {
+      propWrapperFunctions: ['forbidExtraProps']
+    }
   }, {
     code: [
       'class Component extends React.Component {',