fixing a traceback with disco menuitem

see http://nkour.blogspot.com/2005/05/pythons-init-return-none-doesnt-return.html for more

src/config.py

@@ -1600,6 +1600,7 @@ class Service_discovery_window:
 		self.agent_infos = {}
 		if gajim.connections[account].connected < 2:
 			dialogs.Error_dialog(_('You must be connected to browse services'))
+			raise RuntimeError, 'You must be connected to browse services'
 			return
 		xml = gtk.glade.XML(GTKGUI_GLADE, 'service_discovery_window', APP)
 		self.window = xml.get_widget('service_discovery_window')

src/roster_window.py

@@ -1174,8 +1174,12 @@ class Roster_window:
 		if self.plugin.windows[account].has_key('disco'):
 			self.plugin.windows[account]['disco'].window.present()
 		else:
+			try:
 				self.plugin.windows[account]['disco'] = \
 					config.Service_discovery_window(self.plugin, account)
+			except RuntimeError:
+				pass
+				
 
 	def load_iconset(self, path):
 		imgs = {}