Save multiple checkbox on update post meta in wordpress

I have the same problem resolved in:

How to save multiple checkbox on update post meta in wordpress?

I have a cpt (clinica) with a multiple checkbox metabox.

I created the metabox:

add_meta_box('custom-meta-box', 'Music', 'music_meta_box', 'clinica', 'advanced', 'core');

Used the code suggested, but I'm getting the error:

Warning: in_array() expects parameter 2 to be array, boolean given in C:\wamp\www\dwa\wp-content\plugins\network-cliniche\network-cliniche.php on line 86

What am I doing wrong?