Protect against possible null values in $models array.

[mikebronner]

I came across this error today after enabling models collector. (Thanks btw for this awesome feature @reinink!):

get_class() expects parameter 1 to be object, null given (View: /private/var/tmp/homepage-articles.indexmKf4EN)

[reinink]

Weird, I didn't realize that the $models array could contain null values. When does that happen?

[mikebronner]

This happens when I set the $with attribute on a model to include a polymorphic relationship that doesn't always exist.

[barryvdh]

Thanks!