set default sort order

resolves #437

Author: zidhuss

app/src/main/java/com/zeapo/pwdstore/utils/PasswordRepository.java

@@ -280,7 +280,7 @@ public int compare(PasswordItem p1, PasswordItem p2) {
         }
 
         public static PasswordSortOrder getSortOrder(SharedPreferences settings) {
-            return valueOf(settings.getString("sort_order", null));
+            return valueOf(settings.getString("sort_order", FOLDER_FIRST.name()));
         }
     }
 }