[sysadmin-bin] fix crash when group lacks members

[Olav Vitters <ovitters src gnome org>]

commit a72bd46f5e17638365605502811fa27edcd8ffa2
Author: Olav Vitters <olav vitters nl>
Date:   Wed Mar 18 11:50:52 2015 +0100

    fix crash when group lacks members

 mail/export-mail.py |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/mail/export-mail.py b/mail/export-mail.py
index 5012c59..1b4b29b 100755
--- a/mail/export-mail.py
+++ b/mail/export-mail.py
@@ -47,6 +47,9 @@ def fetch_group_members(group):
     members = set()
 
     for _, attr in results:
+        if 'member' not in attr:
+            continue
+
         for userid in attr['member']:
             splitentry = userid.split(',')
             singleentry = splitentry[0]