[PATCH v2 resend] user32: Don't call IsChild with NULL window in EnableWindow

[Marvin]

Hi,

While running your changed tests on Windows, 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=29610

Your paranoid android.


=== w7u (32 bit win) ===
win.c:999: Test failed: wrong dwWindowStatus: 0000 != 0001 active 00A90148 fg 000F0138 in hook HCBT_MINMAX