Blogger embed: Uncaught TypeError: Cannot read property 'length' of null

When I add `<script src='//djlosch.github.io/apollo/apollo.js?verbose=true'/>` to the `<head>` section of Blogger template, the file is loaded, but I see the following error in the browser console

```
Uncaught TypeError: Cannot read property 'length' of null
    at Object.adblocked (apollo.js?verbose=true:129)
    at apollo.js?verbose=true:160
```