libsaria: Fix playlist filtering

The variables "filtered" and "visible" are global, so we need to tell
the function that it shouldn't create local variables.

libsaria/sources/playlist/__init__.py

@@ -20,6 +20,8 @@ def list_ids():
 		yield id
 
 def filter(text):
+	global visible
+	global filtered
 	if len(text) > 0:
 		visible  = playlist.as_set().intersection(library.test_filter(text))
 		filtered = True