While testing the previous commit, it became clear that gourd stems do
not disconnect properly if the gourd disappears while not being dug. A
simple method to create illegal curved stems was to explode the gourd.
This patch changes gourds so that the stem curves back after a gourd is
destroyed, regardless of reason. This hopefully makes curved stems that
are not connected to matching gourds a relict of the past.
56db877360