AppCtx::remove_wnd after paint panic

[sologeek]

Problem
AppCtx::remove_wnd after paint panic

Steps To Reproduce
Steps to reproduce the behavior:

1. Create the second window
2. Render a widget to the second window
3. Remove the second window
4. Panic

Or paste reproducible error codes:

Expected behavior
A clear and concise description of what you expected to happen.

Screenshots
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Environment:

• Ribir version: master
• Rust version: 1.75.0, nightly