Improve reliability of set-constant scriptlet

Related issue:
- https://github.com/uBlockOrigin/uBlock-issues/issues/1694

assets/resources/scriptlets.js

@@ -924,7 +924,9 @@
         const odesc = Object.getOwnPropertyDescriptor(owner, prop);
         let prevGetter, prevSetter;
         if ( odesc instanceof Object ) {
-            if ( odesc.configurable === false ) { return; }
+            if ( odesc.configurable === false ) {
+                owner[prop] = cValue;
+            }
             if ( odesc.get instanceof Function ) {
                 prevGetter = odesc.get;
             }