adding number as a value of "field ID" renders error

If you add pure simple number as "1" or "23" in the "field ID" you get error when the sql tries to make it as a field in the table. The field is not created in the "term_fields_term" table and the "term field" is therefore not working at all.
You probably need to check user input - if he puts only numbers... I guess it will render the same error if it starts with a number, no matter that there are letters after it?
And put it as a rule in the description, not to use numbers like this. Also a simple example in the discription can help like "myfieldname_id" etc.