Fix get_rand_candidate crash

For some reason the loop in get_rand_candidate was exiting earlier than
I thought.  For now, I am returning the last ID looked at to fix the
problem.  I expect there is a better solution, but this seems to work
until I can clean up the collection system.

libsaria/collection/lens.py

@@ -123,13 +123,17 @@ class Playlist(collection.Collection):
 	def get_rand_candidate(self):
 		num      = self.num_visible()
 		next_idx = rand.randint(0, num-1)
-		func = self.visible
+		func = self.walk_filtered_ids
 		if self.filtered == False:
 			func = self.walk_ids
 		for n in func():
 			if next_idx == 0:
 				return n
 			next_idx -= 1
+		# We shouldn't ever get here, but for some reason we are.
+		# We return the last value of n, but I would like to figure
+		# Out why we leave the loop early eventually.
+		return n