do not crash when we remove a contact for which neerby contcts are not in the same accounts. Fixes #8157

src/common/contacts.py

@@ -840,6 +840,8 @@ class MetacontactManager():
             # we want one nearby_family per account
             nearby_family = [data for data in family if account == data['account']]
 
+        if not nearby_family:
+            return (None, None, None)
         big_brother_data = self._get_metacontacts_big_brother(nearby_family)
         big_brother_jid = big_brother_data['jid']
         big_brother_account = big_brother_data['account']

src/roster_window.py

@@ -491,6 +491,8 @@ class RosterWindow:
 
         nearby_family, big_brother_jid, big_brother_account = \
                 self._get_nearby_family_and_big_brother(family, account)
+        if not big_brother_jid:
+            return []
         big_brother_contact = gajim.contacts.get_first_contact_from_jid(
                 big_brother_account, big_brother_jid)