Small null check in DeregisterHandlers.

OpenSim/Framework/Communications/Capabilities/Caps.cs

@@ -220,12 +220,15 @@ namespace OpenSim.Framework.Communications.Capabilities
         /// <param name="path"></param>
         /// <param name="restMethod"></param>
         public void DeregisterHandlers()
+        {
+            if (m_capsHandlers != null)
             {
                 foreach (string capsName in m_capsHandlers.Caps)
                 {
                     m_capsHandlers.Remove(capsName);
                 }
             }
+        }
 
         /// <summary>
         /// Construct a client response detailing all the capabilities this server can provide.