`_post_format_get_terms()` can overwrite names of terms in other taxonomies

[dlh]

_post_format_get_terms() filters 'get_terms' and includes this logic:

if ( in_array( 'post_format', (array) $taxonomies ) ) {
	if ( isset( $args['fields'] ) && 'names' == $args['fields'] ) {
		foreach ( $terms as $order => $name ) {
			$terms[$order] = get_post_format_string( str_replace( 'post-format-', '', $name ) );
		}
	}
...

which affects the names of all $terms, as long as post_format was one of the queried taxonomies. Many terms are replaced with an empty string from get_post_format_string().

The attached patch includes a test to demonstrate the issue, and it would check before changing a value that the value begins with post-format- and that get_post_format_string() returns a name for the value.