Auto merge of #24818 - gterzian:fix_panic_on_finish_load, r=jdm

Prevent panic on layout send in finish-load

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Do not run the finish load steps if the pipeline has been discarded by the time the parser finishes.

---
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- [ ] `./mach build -d` does not report any errors
- [ ] `./mach test-tidy` does not report any errors
- [ ] These changes fix #22955 (GitHub issue number if applicable)

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

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components/script/script_thread.rs

@@ -2847,6 +2847,14 @@ impl ScriptThread {
 
         let document = self.documents.borrow_mut().remove(id);
 
+        // Abort the parser, if any,
+        // to prevent any further incoming networking messages from being handled.
+        if let Some(document) = document.as_ref() {
+            if let Some(parser) = document.get_current_parser() {
+                parser.abort();
+            }
+        }
+
         // We should never have a pipeline that's still an incomplete load,
         // but also has a Document.
         debug_assert!(idx.is_none() || document.is_none());