fix bugs for first-time user (no plist)
diff --git a/settingdialog.ui b/settingdialog.ui
index b848aa9..d805198 100644
--- a/settingdialog.ui
+++ b/settingdialog.ui
@@ -42,7 +42,7 @@
                 </widget>
               </item>
               <item>
-                <widget class="QLabel">
+                <widget class="QLabel" name="prefixLabel">
                   <property name="text">
                     <string>Prefix</string>
                   </property>