Also handle partial timelapse settings gracefully

Server startup could fail if for whatever reason the timelapse settings
had lost their type value, since the dict was not merged with the
default values upon retrieval.

src/octoprint/timelapse.py

@@ -68,7 +68,7 @@ def configureTimelapse(config=None, persist=False):
 	global current
 
 	if config is None:
-		config = settings().get(["webcam", "timelapse"])
+		config = settings().get(["webcam", "timelapse"], merged=True)
 
 	if current is not None:
 		current.unload()