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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components/script/dom/document.rs

@@ -367,6 +367,9 @@ impl Document {
         self.loader.borrow_mut()
     }
 
+    #[inline]
+    pub fn has_browsing_context(&self) -> bool { self.has_browsing_context }
+
     /// https://html.spec.whatwg.org/multipage/#concept-document-bc
     #[inline]
     pub fn browsing_context(&self) -> Option<Root<BrowsingContext>> {