Poster image not preprocessed correctly

In template_preprocess_videojs_formatter_videojs(), the $vars['items']['thumbnail'] variable that is derived from content-type-level $poster_image is referencing the field's filepath string directly. This must be incorrect, as the rest of the code expects this variable to be an array that represents the file object. Consequently, this causes multiple errors:

- and
get rendered in the template, which causes IE to puke.
- PHP notices under strict mode, alerting that a string is wrongfully being used as an array in multiple areas.
- $vars['poster'] derived from the 'thumbnail' string always fails and returns an empty string in the template for the video element's poster attribute.