deleting metadata elements is unsupported
just a note that deleting metadata elements from their sets
is possible in theory, as there is a delete button in the ZMI,
but this feature is virtually unsupported.
Any object which uses the metadata set will not render after the deletion,
but raise an AttributeError. Thus deletion is only possible
if the set is not (yet) in use.
If one ever deletes a Metadata element, the fix is to readd it.
Instead of deleting metadata elements it is possible to disable
them via their field tab, so I feel there exists an acceptable
File this as "wish" as so far nobody has complained about this,
there is an easy workaround and I do not plan to fix it.
If anyone finds a non-obfuscated way to fix it I think those patches
are wellcome ...
Of, and of course please resolve this one if its only me
who can reproduce the issue.