defaultCountryCode can't be empty (at least for now)

CHANGELOG.md

@@ -2,6 +2,7 @@
 
 ## Unreleased
 
+- An `InvalidConfigException` is now thrown if the `defaultCountryCode` config setting is set to an empty string. ([#15812](https://github.com/craftcms/cms/pull/15812))
 - Fixed an error that could occur when saving an element, if a Date field’s time zone input was focused.
 - Fixed a bug where the time zones listed in Date fields weren’t labelled properly based on the selected date. ([#15805](https://github.com/craftcms/cms/issues/15805))
 - Fixed a missing authorization vulnerability.

src/config/GeneralConfig.php

@@ -3963,6 +3963,10 @@ public function defaultCookieDomain(string $value): self
      */
     public function defaultCountryCode(string $value): self
     {
+        if (empty($value)) {
+            throw new InvalidConfigException('`defaultCountryCode` cannot be empty', 0);
+        }
+
         $this->defaultCountryCode = $value;
         return $this;
     }