plugin ad-hoc D-Bus: fixed warning when no media player is found

sat/memory/disco.py

@@ -313,7 +313,8 @@ class Discovery(object):
         """Return entities (including jid_ and its items) offering features
 
         @param features: iterable of features which must be present
-        @param identity(None, tuple(unicode, unicode)): if not None, accept only this (category/type) identity
+        @param identity(None, tuple(unicode, unicode)): if not None, accept only this
+            (category/type) identity
         @param jid_: the jid of the target server (None for profile's server)
         @param profile: %(doc_profile)s
         @return: a set of found entities

sat/plugins/plugin_adhoc_dbus.py

@@ -346,6 +346,8 @@ class AdHocDBus(object):
                                                           NS_MEDIA_PLAYER, timeout=5)
                             command_elt = self._c.getCommandElt(result_elt)
                             form = data_form.findForm(command_elt, NS_MEDIA_PLAYER)
+                            if form is None:
+                                continue
                             mp_options = form.fields['media_player'].options
                             session_id = command_elt.getAttribute('sessionid')
                             if mp_options and session_id: