MSHTML: fix blank.htm resources

[Jacek Caban]

Alexandre Julliard wrote:

>That's a feature ;-)  We can't support loading builtins as datafiles,
>so the idea is that it's more likely that the app will be happy with
>loading the native as datafile than loading the builtin in normal
>mode. It does make the behavior a bit surprising I agree.
>
>  
>
Good to know that Wine doesn't have such bug in so
important place:-) Maybe it would be better to point
it out somewhere in the documentation so that people
like me won't have to cover such things themselves.

Thanks,
    Jacek