validation method added

src/main/java/ru/touchin/templates/model/GoogleJsonModel.java

@@ -33,4 +33,10 @@ public abstract class GoogleJsonModel extends Model {
         }
     }
 
+    protected static void validateNullOrNonEmpty(@Nullable final Object object) throws ValidationException {
+        if (object != null && isNullOrEmpty(object)) {
+            throw new ValidationException("Nullable or not empty object is empty");
+        }
+    }
+
 }