[PATCH] mshtml: Fix NULL offset parent handling in HTMLElement_get_offsetParent()

[Marvin]

Hi,

While running your changed tests, I think I found new failures.
Being a bot and all I'm not very good at pattern recognition, so I might be
wrong, but could you please double-check?

Full results can be found at:
https://testbot.winehq.org/JobDetails.pl?Key=87842

Your paranoid android.

=== w8 (32 bit report) ===

mshtml:
0c6c:dom: unhandled exception c0000005 at 770A576E