Cast fix (#4939)

* Update frontend

* Fix exception on cast startup

homeassistant/components/frontend/version.py

@@ -2,7 +2,7 @@
 
 FINGERPRINTS = {
     "core.js": "ad1ebcd0614c98a390d982087a7ca75c",
-    "frontend.html": "920bb20410f9a1b8458600b15a1d40ae",
+    "frontend.html": "826ee6a4b39c939e31aa468b1ef618f9",
     "mdi.html": "46a76f877ac9848899b8ed382427c16f",
     "micromarkdown-js.html": "93b5ec4016f0bba585521cf4d18dec1a",
     "panels/ha-panel-dev-event.html": "c2d5ec676be98d4474d19f94d0262c1e",

homeassistant/components/frontend/www_static/home-assistant-polymer

@@ -1 +1 @@
-Subproject commit b8a7c6624d54d3f579ff22079c9dc01843a0fc6e
+Subproject commit b5c3575cb5f284178e52d75db24c46131afb4cfa

homeassistant/components/media_player/cast.py

@@ -236,9 +236,9 @@ class CastDevice(MediaPlayerDevice):
     @property
     def media_position(self):
         """Position of current playing media in seconds."""
-        if self.media_status is None or not (
-                self.media_status.player_is_playing or
-                self.media_status.player_is_idle):
+        if self.media_status is None or self.media_status_received is None or \
+                not (self.media_status.player_is_playing or
+                     self.media_status.player_is_idle):
             return None
 
         position = self.media_status.current_time