Destroying a non-top modal window leaves a dangling pointer

[tintinhamans]

Prerequisites

• I have searched for similar issues and confirmed this is not a duplicate

Game Version

• Command & Conquer Generals
• Command & Conquer Generals: Zero Hour

Bug Description

Destroyed windows are only removed from the modal stack when they are on top.

For example, with a stack of B → A, destroying A leaves B → freed A. When B closes, the freed pointer becomes the stack head. The next mouse event calls winPointInChild() on it and crashes.

Destroyed windows should be removed from the entire modal stack.

Reproduction Steps

1. Open modal window A.
2. Open modal window B above it.
3. Destroy A while B remains open.
4. Close B.
5. Move the mouse.

Additional Context

This was observed with 0xDEADBEEF passed to GameWindow::winPointInChild(). The affected modal cleanup exists in both the Generals and Zero Hour window managers.

[tintinhamans]

@bobtista, @mirelle7: seems like you guys stumbled into this one but couldn't find a PR (mirelle7@4b8a6c0)