Merge pull request #394 from jasonlaw/master

Translation return null value when no entry found

@@ -655,6 +655,16 @@ class GetImpl implements GetService {
     translations.addAll(tr);
   }
 
+  void appendTranslations(Map<String, Map<String, String>> tr) {
+    tr.forEach((key, map) {
+      if (Get.translations.containsKey(key)) {
+        Get.translations[key].addAll(map);
+      } else {
+        Get.translations[key] = map;
+      }
+    });
+  }
+
   void changeTheme(ThemeData theme) {
     getxController.setTheme(theme);
   }

@@ -257,15 +257,22 @@ abstract class Translations {
 
 extension Trans on String {
   String get tr {
+    // Returns the key if locale is null.
     if (Get.locale?.languageCode == null) return this;
-    if (Get.translations
-        .containsKey("${Get.locale.languageCode}_${Get.locale.countryCode}")) {
+    
+    // Checks whether the language code and country code are present, and whether the key is also present.
+    if (Get.translations.containsKey(
+            "${Get.locale.languageCode}_${Get.locale.countryCode}") &&
+        Get.translations["${Get.locale.languageCode}_${Get.locale.countryCode}"]
+            .containsKey(this)) {
       return Get.translations[
           "${Get.locale.languageCode}_${Get.locale.countryCode}"][this];
-    } else if (Get.translations.containsKey(Get.locale.languageCode)) {
+    
+    // Checks if there is a callback language in the absence of the specific country, and if it contains that key.  
+    } else if (Get.translations.containsKey(Get.locale.languageCode) &&
+        Get.translations[Get.locale.languageCode].containsKey(this)) {
       return Get.translations[Get.locale.languageCode][this];
-    } else if (Get.translations.isNotEmpty) {
-      return Get.translations.values.first[this];
+    // If there is no corresponding language or corresponding key, return the key.
     } else {
       return this;
     }