Using FDocument after THtmlView.Clear crash if FDocument is nil.

[manliomazzon]

I'm not 100% sure of this, but I think that if you call Clear, FDocument becomes nil, and in a few other places FDocument is used without checking if it is nil.

Therefore, because FDocument can be nil, you should always check FDocument <> nil before using it, or before trying to destroy it.

I had these crashes until I changed the code to always check FDocument<>nil before using it, and the crashes stopped.