Fix uninitialized memory bug in GdiEngine

[lhecker]

ed27737 contains a regression were a RECT in GdiEngine wasn't properly
initialized anymore. Due to this, rendering during scrolling behaved erratic.

To find other cases of this bug in ed27737 the following regex was used:

^-.* = \{\s*\d*\s*\};

It appears that only GdiEngine was affected by a bug of this kind,
but just to be sure, this PR reverts all other instances.
This bug was likely caused when I tried to undo some of the changes in
ed27737 to make the PR smaller, but failed to revert the code properly.

PR Checklist

• Closes Weird scrolling regression in the GDI renderer #13270
• I work here

Validation Steps Performed

I'm unable to reproduce the issue on my hardware and am unable to test
this change, but the uninitialized struct is clearly a bug regardless.

Co-authored-by: James Holderness [email protected]

[lhecker]

I still have this weird "ghosting" effect when I scroll in my Windows 10 VM, but I'm fairly confident that this should fix the bug.
If you happen to get a chance, would you mind checking whether initializing the RECT properly fixes the bug, @j4james? (If you haven't done so already.)

[DHowett]

How did the audit build miss this?

[j4james]

Yep, this fixes it for me. Thanks.

[lhecker]

How did the audit build miss this?

That project doesn't get built in the AuditMode configuration. 😿

[lhecker]

How did the audit build miss this?

@DHowett Terrifying fun fact: I made RendererGdi compile under AuditMode and this bug doesn't get caught at all.
(Sorry, I posted this accidentally on the issue first.)

[ghost]

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