Fix a few

websocket-sharp/Ext.cs

@@ -261,7 +261,8 @@ namespace WebSocketSharp
     internal static string CheckIfValidProtocols (this string [] protocols)
     {
       return protocols.Contains (
-               protocol => protocol.Length == 0 || !protocol.IsToken ())
+               protocol =>
+                 protocol == null || protocol.Length == 0 || !protocol.IsToken ())
              ? "Contains an invalid value."
              : protocols.ContainsTwice ()
                ? "Contains a value twice."

websocket-sharp/Server/WebSocketService.cs

@@ -157,7 +157,10 @@ namespace WebSocketSharp.Server
       }
 
       set {
-        if (State == WebSocketState.CONNECTING && value.IsToken ())
+        if (State == WebSocketState.CONNECTING &&
+            value != null &&
+            value.Length > 0 &&
+            value.IsToken ())
           _protocol = value;
       }
     }