libsaria: Clear cur_id correctly

I do this if the song isn't found in the library, rather than as part of
opening a track from disk.

libsaria/path/files.py

@@ -24,7 +24,6 @@ def open_xml(file):
 
 def open_music(file):
 	try:
-		libsaria.sources.cur_id = None
 		libsaria.controls.load(file)
 		libsaria.controls.play()
 	except Exception, e:

libsaria/sources/__init__.py

@@ -41,10 +41,12 @@ get_attrs_id = library.get_attrs
 
 def get_attrs(*attrs):
 	# I should probably get a lock here...
+	global cur_id
 	res = None
 	if cur_id:
 		res = get_attrs_id(cur_id, *attrs)
 	if res == None:
+		cur_id = None
 		file = libsaria.audio.get_cur_file()
 		res = find_attrs(file, *attrs)
 	if res == None: