fix: replace empty string namespaceURI with null (#1285)

Temp fix before the CDP fix crrev.com/c/4856861 is landed

---------

Co-authored-by: Maksim Sadym <[email protected]>

src/bidiMapper/domains/script/Realm.ts

@@ -170,6 +170,10 @@ export class Realm {
       ) {
         bidiValue.shadowRoot = this.#deepSerializedToBiDi(bidiValue.shadowRoot);
       }
+      // `namespaceURI` can be is either `null` or non-empty string.
+      if (bidiValue.namespaceURI === '') {
+        bidiValue.namespaceURI = null;
+      }
     }
 
     // Recursively update the nested values.