Updated Speech Input Handler

Added early out if no keywords exists

Author: StephenHodgson

Assets/HoloToolkit/Input/Scripts/Editor/SpeechInputHandlerEditor.cs

@@ -52,6 +52,9 @@ private void ShowList(SerializedProperty list)
 
             // remove the keywords already assigned from the registered list
             SpeechInputHandler handler = (SpeechInputHandler)target;
+            
+            if (handler.keywords == null) { return; }
+            
             string[] availableKeywords = registeredKeywords.Except(handler.keywords.Select(keywordAndResponse => keywordAndResponse.Keyword)).ToArray();
 
             // keyword rows