prevent remove all servers

ShadowsocksX-NG/Base.lproj/PreferencesWindowController.xib

@@ -16,6 +16,7 @@
                 <outlet property="profileBox" destination="oZ5-85-pwY" id="D19-PQ-X7E"/>
                 <outlet property="profilesTableView" destination="r91-ho-Lum" id="TNk-f6-Vgo"/>
                 <outlet property="remarkTextField" destination="q3C-S0-iNn" id="DSv-lV-PX7"/>
+                <outlet property="removeButton" destination="3ei-2f-kHB" id="DdP-dA-coT"/>
                 <outlet property="window" destination="F0z-JX-Cv5" id="gIp-Ho-8D9"/>
             </connections>
         </customObject>

ShadowsocksX-NG/PreferencesWindowController.swift

@@ -26,6 +26,7 @@ class PreferencesWindowController: NSWindowController
     
     @IBOutlet weak var copyURLBtn: NSButton!
     
+    @IBOutlet weak var removeButton: NSButton!
     let tableViewDragType: String = "ss.server.profile.data"
     
     var defaults: NSUserDefaults!
@@ -33,6 +34,7 @@ class PreferencesWindowController: NSWindowController
     
     var editingProfile: ServerProfile!
 
+
     override func windowDidLoad() {
         super.windowDidLoad()
 
@@ -64,6 +66,7 @@ class PreferencesWindowController: NSWindowController
     
     @IBAction func addProfile(sender: NSButton) {
         if editingProfile != nil && !editingProfile.isValid(){
+            shakeWindows()
             return
         }
         profilesTableView.beginUpdates()
@@ -131,6 +134,12 @@ class PreferencesWindowController: NSWindowController
     }
     
     func updateProfileBoxVisible() {
+        if profileMgr.profiles.count == 1 {
+            removeButton.enabled = false
+        }else{
+            removeButton.enabled = true
+        }
+
         if profileMgr.profiles.isEmpty {
             profileBox.hidden = true
         } else {