Fixed: Testing SABnzbd when no categories are configured

(cherry picked from commit 0e31281828c737e3f6eecbb870960194888a970a)

src/NzbDrone.Core/Download/Clients/Sabnzbd/SabnzbdCategory.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using Newtonsoft.Json;
 using NzbDrone.Common.Disk;
 using NzbDrone.Core.Download.Clients.Sabnzbd.JsonConverters;
@@ -7,10 +7,14 @@ namespace NzbDrone.Core.Download.Clients.Sabnzbd
 {
     public class SabnzbdConfig
     {
-        public SabnzbdConfigMisc Misc { get; set; }
+        public SabnzbdConfig()
+        {
+            Categories = new List<SabnzbdCategory>();
+            Servers = new List<object>();
+        }
 
+        public SabnzbdConfigMisc Misc { get; set; }
         public List<SabnzbdCategory> Categories { get; set; }
-
         public List<object> Servers { get; set; }
     }