refactor: default date and timestamp format returned by Defaults

src/QUI/ERP/Defaults.php

@@ -197,7 +197,7 @@ public static function getTimestampFormat($lang = false)
 
         $value = $Config->get('timestampFormat', $lang);
 
-        if ($value !== false) {
+        if (!empty($value)) {
             self::$timestampFormat[$lang] = $value;
         }
 
@@ -233,7 +233,7 @@ public static function getDateFormat($lang = false): string
 
         $value = $Config->get('dateFormat', $lang);
 
-        if ($value !== false) {
+        if (!empty($value)) {
             self::$dateFormat[$lang] = $value;
         }