Make sure structure for wake word exist before use

==== Fixed Issues ====
#1105

====  Tech Notes ====
Verify that the sub-config for the set wake word exist before writing to
it.

mycroft/client/speech/listener.py

@@ -221,6 +221,8 @@ class RecognizerLoop(EventEmitter):
         phonemes = self.config.get("phonemes")
         thresh = self.config.get("threshold")
         config = self.config_core.get("hotwords", {word: {}})
+        if word not in config:
+            config[word] = {}
         if phonemes:
             config[word]["phonemes"] = phonemes
         if thresh: