script#edit shouldn't allow users to remove all select options.

[johrstrom]

When adding and removing select options - users should not be allowed to remove all the options. this may require #2948 to be implemented (though I don't know that for sure).

In any case - users should be able to whittle the list down to 1 at which point it becomes fixed, but they shouldn't be able to get to 0.

[johrstrom]

This was semi fixed in #3054 - but I still want to keep it open to deal with #2948.

So instead of showing an alert - we enable the very last option as a static option when #2958 is complete.