Steps to reproduce:

1. Launch a ship with Telemachus and MechJeb
2. In map view, set a target
3. Select Telemachus (part) -> "Open Link"
4. In /telemachus/console.html, add any of "Docking X angle," "Relative Pitch Angle", "Docking z angle"

Expected result:

Docking x, y, or z appear (in degrees)

Observed result:

UI shows "No Signal Found." In terms of RPCs, the client sees the following:

Request URL: http://127.0.0.1:8085/telemachus/datalink?p=p.paused&a0=t.universalTime&a1=v.missionTime&a2=r.resource[ElectricCharge]&a3=s.sensor.pres&a4=s.sensor.temp&a5=r.resourceMax[ElectricCharge]&a6=dock.x&a7=dock.y&a8=tar.distance&a9=dock.az
Response code: 500

Response body:

Internal Server Error 500

Object reference not set to an instance of an object   at Telemachus.DockingDataLinkHandler.update () [0x00000] in :0 
  at Telemachus.DockingDataLinkHandler.<.ctor>b__2 (Telemachus.DataSources dataSources) [0x00000] in :0 
  at Telemachus.DataLinkResponsibility.argumentsParse (System.String args, Telemachus.DataSources dataSources) [0x00000] in :0 
  at Telemachus.DataLinkResponsibility.process (Servers.AsynchronousServer.ClientConnection cc, Servers.MinimalHTTPServer.HTTPRequest request) [0x00000] in :0 
  at Servers.MinimalHTTPServer.Server.processRequest (Servers.AsynchronousServer.ClientConnection cc, Servers.MinimalHTTPServer.HTTPRequest request) [0x00000] in :0 
  at Servers.MinimalHTTPServer.ClientConnection.StatefulConnectionRead (System.Object sender, Servers.ConnectionEventArgs e) [0x00000] in :0 

Clarification:

After additional testing, I've discovered that the angles appear if the target docking port is selected on the destination ship; if a target is selected but there is no docking port selected, the 500 error appears. I suspect the 500 errors are traceable to DataLinkHandlers.cs:856; investigating further.

Thank you for pulling in the changes! Looks good now.