Issue #3481616: Error in CountryCacheContext if no country is set.

Closes #3481616

src/Cache/Context/CountryCacheContext.php

@@ -41,7 +41,9 @@ class CountryCacheContext implements CacheContextInterface {
    * {@inheritdoc}
    */
   public function getContext() {
-    return $this->currentCountry->getCountry()->getCountryCode();
+    // In case the current country cannot be determined, return "none" as the
+    // cache context.
+    return $this->currentCountry->getCountry()?->getCountryCode() ?? 'none';
   }
 
   /**