MindTouch.Deki.Script.DekiScriptInvokeException: function 'uri.encode' failed

Server stack trace: 
  at MindTouch.Deki.Script.DekiScriptRuntime+<Invoke>d__0.MoveNext () [0x00000] 
  at MindTouch.Dream.Coroutine.Iterate (IEnumerator`1 coroutine, MindTouch.Tasking.TaskEnv env, System.Action`1 completion) [0x00000] 

Exception rethrown at [0]: 
 ---> System.ArgumentException: missing value for parameter 'text' (index 0)
  at MindTouch.Deki.DekiScriptFunction+DekiScriptInvokeDelegateWrapper.Invoke (MindTouch.Deki.Script.DekiScriptLiteral arguments) [0x00000] 
  at MindTouch.Deki.DekiScriptFunctionNative.Invoke (MindTouch.Deki.Script.DekiScriptLiteral arguments) [0x00000] 
  at MindTouch.Deki.Script.DekiScriptRuntime+<Invoke>d__0.MoveNext () [0x00000] --- End of inner exception stack trace ---

  at MindTouch.Deki.Script.DekiScriptRuntime+<Invoke>d__0.MoveNext () [0x00000] 
  at MindTouch.Dream.Coroutine.Iterate (IEnumerator`1 coroutine, MindTouch.Tasking.TaskEnv env, System.Action`1 completion) [0x00000]