fix(web): prevent clearing fallback header

If the cookie fallback isn't set in local storage, the X-Fallback-Cookies header is set to empty even if the default header has some value set. This change will only set the header if there's a value in local storage to allow developer to set the fallback header if they have a value from somewhere else.

Author: stnguyen90

templates/web/src/client.ts.twig

@@ -353,7 +353,10 @@ class Client {
         };
 
         if (typeof window !== 'undefined' && window.localStorage) {
-            headers['X-Fallback-Cookies'] = window.localStorage.getItem('cookieFallback') ?? '';
+            const cookieFallback = window.localStorage.getItem('cookieFallback');
+            if (cookieFallback) {
+                headers['X-Fallback-Cookies'] = cookieFallback;
+            }
         }
 
         if (method === 'GET') {