# HG changeset patch
# User Paul Boddie <paul@boddie.org.uk>
# Date 1445359122 -7200
# Node ID bfcc8db523fd6efefc665e7459087fffe504cbfd
# Parent  e288b996492be2ceb7c4c7881ef7b2f297aa0d61
Fixed exception period updates.

diff -r e288b996492b -r bfcc8db523fd imiptools/data.py
--- a/imiptools/data.py	Tue Oct 20 18:01:13 2015 +0200
+++ b/imiptools/data.py	Tue Oct 20 18:38:42 2015 +0200
@@ -483,12 +483,12 @@
         removed corresponding to those periods.
         """
 
-        old_exdates = self.get_date_value_item_periods("EXDATE")
+        old_exdates = self.get_date_value_item_periods("EXDATE") or []
         new_exdates = set(old_exdates)
         new_exdates.update(excluded)
         new_exdates.difference_update(asserted)
 
-        if not new_exdates:
+        if not new_exdates and self.has_key("EXDATE"):
             del self["EXDATE"]
         else:
             self["EXDATE"] = []