Reference error document undefined

[mstrofbass]

This is a possible, temporary solution for the defect discussed in #2583.

Simply checking if document exists should clear up the error.

[raineorshine]

UPDATE: I see this may no longer be needed if #2624 fixes the issue.

Yes, I suppose that hiding the issue is better than having to revert the previous test changes that introduces the async issue.

Could you add a console.warn when document is undefined? That will avoid entirely brushing the problem under the rug and allow us to notice if it is still an issue in the future.