Auto merge of #14159 - upsuper:media-query, r=Wafflespeanut

Allow empty media query list

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- [x] `./mach test-tidy` does not report any errors
- [ ] These changes fix #__ (github issue number if applicable).

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components/script/dom/htmllinkelement.rs

@@ -359,8 +359,7 @@ impl FetchResponseListener for StylesheetContext {
                                                    Some(environment_encoding), Origin::Author,
                                                    win.css_error_reporter(),
                                                    ParserContextExtraData::default());
-            let media = self.media.take().unwrap();
-            sheet.set_media(Some(media));
+            sheet.set_media(self.media.take().unwrap());
             let sheet = Arc::new(sheet);
 
             let win = window_from_node(&*elem);

components/script/dom/htmlmetaelement.rs

@@ -83,7 +83,7 @@ impl HTMLMetaElement {
                     *self.stylesheet.borrow_mut() = Some(Arc::new(Stylesheet {
                         rules: vec![CSSRule::Viewport(Arc::new(RwLock::new(translated_rule)))],
                         origin: Origin::Author,
-                        media: None,
+                        media: Default::default(),
                         // Viewport constraints are always recomputed on resize; they don't need to
                         // force all styles to be recomputed.
                         dirty_on_viewport_size_change: false,

components/script/dom/htmlstyleelement.rs

@@ -65,8 +65,7 @@ impl HTMLStyleElement {
         let mut sheet = Stylesheet::from_str(&data, url, Origin::Author, win.css_error_reporter(),
                                              ParserContextExtraData::default());
         let mut css_parser = CssParser::new(&mq_str);
-        let media = parse_media_query_list(&mut css_parser);
-        sheet.set_media(Some(media));
+        sheet.set_media(parse_media_query_list(&mut css_parser));
         let sheet = Arc::new(sheet);
 
         win.layout_chan().send(Msg::AddStylesheet(sheet.clone())).unwrap();