Auto merge of #15359 - freeatnet:15332-macroed-event-handlers-check-for-window, r=KiChjang

Event handlers forwarded to a window check for window presence

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This change adds a check for the presence of a window in event handlers of `body` and `frameset` that are forwarded to the window.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #15332

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- [x] There are tests for these changes OR
- [ ] These changes do not require tests because _____

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I'm new to both Servo and Rust — so any suggestions for improvement are very welcome.

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