Auto merge of #23886 - servo:jdm-patch-46, r=asajeffrey

Avoid panic during shutdown when Blobs exist

Observed when closing the UWP app when https://www.joshmatthews.net/demos/lamp.html is the active document.

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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 do not require tests because no real shutdown tests.

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components/script/dom/blob.rs

@@ -296,7 +296,7 @@ impl Blob {
 
             let msg = FileManagerThreadMsg::DecRef(f.id.clone(), origin, tx);
             self.send_to_file_manager(msg);
-            let _ = rx.recv().unwrap();
+            let _ = rx.recv();
         }
     }