Doesn’t work with WP 4.7

Hi there!

First of all, thank you very much for your amazing plugin!

I just updated my WP Version to 4.7, and now the pluging throws a lot of errors:

Warning: Illegal offset type in [...]/wp-content/plugins/custom-taxonomy-order-ne/customtaxorder.php on line 207
Warning: Illegal offset type in [...]/wp-content/plugins/custom-taxonomy-order-ne/customtaxorder.php on line 209
[...]

I seems to have something to do with the taxonomy being an array now. When I insert this just after line 207 in your customtaxorder.php:

var_dump( $taxonomy )

…it gives me back this:

array(1) {
  [0]=>string(22) "my-taxonomy"
}

…when it should be a string, right?
Can you have a look?