Apparently it is possible to have chm file without #STRINGS in it, so we should not stop processing file at it. Fixes bug #12498

[Juan Lang]

>  Have you tried patch without this "if"? In my case it crashes without it
>  when I try to open chm from bug #12498... i don't know if strdupW can
>  dup NULL as well as null?

Aaaah...  Sorry, my mistake, I missed this declaration:
        static const WCHAR null[] = {0};
That solves that mystery.

In that case, one fix per patch, please.  This fix and the other are
unrelated:  one fixes a crash, the other deals with a missing #STRINGS
stream.  Thanks,
--Juan