Fix update crash in case of unset dates in APK

fdroidserver/update.py

@@ -568,11 +568,15 @@ def scan_apks(apps, apkcache, repodir, knownapks):
             # has to be more than 24 hours newer because ZIP/APK files do not
             # store timezone info
             manifest = apkzip.getinfo('AndroidManifest.xml')
+            if manifest.date_time[1] == 0:  # month can't be zero
+                logging.debug('AndroidManifest.xml has no date')
+            else:
                 dt_obj = datetime(*manifest.date_time)
                 checkdt = dt_obj - timedelta(1)
                 if datetime.today() < checkdt:
                     logging.warn('System clock is older than manifest in: '
-                             + apkfilename + '\nSet clock to that time using:\n'
+                                 + apkfilename
+                                 + '\nSet clock to that time using:\n'
                                  + 'sudo date -s "' + str(dt_obj) + '"')
 
             iconfilename = "%s.%s.png" % (