Enable removal of optional recurrence for personal-events

Alternativly the frontend would need to always send the empty string.

aleksis/core/schema/personal_event.py

@@ -110,3 +110,12 @@ class PersonalEventBatchPatchMutation(BaseBatchPatchMutation):
         if info.context.user.has_perm("core.edit_personal_event_rule", obj):
             return []
         return cls._meta.permissions
+
+    @classmethod
+    def before_mutate(cls, root, info, input):  # noqa
+        for event in input:
+            # Remove recurrences if none were received.
+            if not "recurrences" in event:
+                event["recurrences"] = ""
+
+        return input