Leaving the 'Frequency' pulldown at default causes data loss

When creating a repeating event, if one forgets to set the Frequency pulldown to 'Every',
all the date info associated with the node is lost.

This can be traumatic if one has typed a lot of info in,
and it's hard for a user who has fallen into this trap
to figure out what they did wrong.

The module should probably treat an unchanged Frequency pulldown as meaning 'Every'.