[directive-restrict] Finding ancestor functions assumes that all functions have names

Crashes when finding ancestor functions if ancestor function does not have a name.

Can reproduce by linting the following file:

```
export default function () {
return {
restrict: 'E',
}
}
```

Error message and stack trace are:

```
Cannot read property 'name' of null
TypeError: Cannot read property 'name' of null
at ./node_modules/eslint-plugin-angular/rules/directive-restrict.js:62:50
at Array.some ()
at checkLiteralNode (./node_modules/eslint-plugin-angular/rules/directive-restrict.js:59:40)
at Property (./node_modules/eslint-plugin-angular/rules/directive-restrict.js:143:17)
at listeners.(anonymous function).forEach.listener (./node_modules/eslint/lib/util/safe-emitter.js:47:58)
at Array.forEach ()
at Object.emit (./node_modules/eslint/lib/util/safe-emitter.js:47:38)
at NodeEventGenerator.applySelector (./node_modules/eslint/lib/util/node-event-generator.js:251:26)
at NodeEventGenerator.applySelectors (./node_modules/eslint/lib/util/node-event-generator.js:280:22)
at NodeEventGenerator.enterNode (./node_modules/eslint/lib/util/node-event-generator.js:299:14)
```