rustdoc: Handle null localStorage value

Author: Chad Norvell

src/librustdoc/html/static/js/storage.js

@@ -28,7 +28,11 @@ function getSettingValue(settingName) {
     // This prevents an injection vulnerability where someone could plant
     // JS code into the localStorage value, which could be executed when
     // we pull it out.
-    return current.replace(/[\s()[\]{}*"'`<>.:;=&|]/g,"");
+    if (current) {
+        return current.replace(/[\s()[\]{}*"'`<>.:;=&|]/g,"");
+    }
+
+    return null;
 }
 
 const localStoredTheme = getSettingValue("theme");