wp_update_term - Check return from get_term in case it's a WP Error

[simonwheatley]

Currently the code in wp_update_term doesn't check the returned term from get_term, which could be a WP_Error object. add_magic_quotes on the next line doesn't like WP_Error objects.

[simonwheatley]

Code within wp_update_term to check whether the return from get_term is a WP_Error, and return it immediately if it is.

[ryan]

(In [10803]) Check if error. Props simonwheatley. fixes #9345