Handle clean shutdown when task not running

Author: jjlawren

plexwebsocket.py

@@ -153,4 +153,5 @@ def player_event(self, msg):
     def close(self):
         """Close the listening websocket."""
         self._active = False
-        self._current_task.cancel()
+        if self._current_task is not None:
+            self._current_task.cancel()

setup.py

@@ -3,7 +3,7 @@
 with open('README.md') as f:
     long_description = f.read()
 
-VERSION="0.0.6"
+VERSION="0.0.7"
 
 setup(
     name='plexwebsocket',