fix android config

lib/localization/app_translations.dart

@@ -28,15 +28,15 @@ class AppTranslations {
   get currentLanguage => locale.languageCode;
 
   String text(String key, {List<String>? translationVariables}) {
-    String value = _localisedValues[key];
+    String? value = _localisedValues[key];
     if (value == null) {
       return "$key not found";
     }
     if (translationVariables != null) {
       translationVariables.asMap().forEach((i, s) {
-        value = value.replaceAll("{$i}", s);
+        value = value!.replaceAll("{$i}", s);
       });
     }
-    return value;
+    return value!;
   }
 }