oc-calendar: Fix weekly recurring events exported to Outlook from SOGo

SOGo does not create BYDAY mask in weekly recurrence, so
we have to guess it from the start date's day of week.

In other case, the event is not exported to Outlook and it
says that is corrupted.

NEWS

@@ -5,6 +5,7 @@ Enhancements
  - Improve sync speed from Outlook by non-reprocessing already downloaded unread mails
 
 Bug fixes
+ - Weekly recurring events created in SOGo web interface are now shown in Outlook
  - Fix exception modifications import in recurrence series
  - Sent mails are not longer in Drafts folder using Outlook
  - Fix server side crash parsing rtf emails with images (with word97 format)

OpenChange/MAPIStoreRecurrenceUtils.m

@@ -325,15 +325,25 @@
       rp->RecurFrequency = RecurFrequency_Weekly;
       rp->PatternType = PatternType_Week;
       rp->Period = repeatInterval;
+
+      dayOfWeek = [startDate dayOfWeek];
+
       mask = 0;
       byDayMask = [self byDayMask];
-      for (count = 0; count < 7; count++)
-        if ([byDayMask occursOnDay: count])
-          mask |= 1 << count;
+      if (byDayMask)
+        {
+          for (count = 0; count < 7; count++)
+            if ([byDayMask occursOnDay: count])
+              mask |= 1 << count;
+        }
+      else
+        {
+          /* Set the recurrence pattern using start date */
+          mask |= 1 << dayOfWeek;
+        }
       rp->PatternTypeSpecific.WeekRecurrencePattern = mask;
 
       /* FirstDateTime */
-      dayOfWeek = [startDate dayOfWeek];
       if (dayOfWeek)
         beginOfWeek = [startDate dateByAddingYears: 0 months: 0
                                               days: -dayOfWeek