Web browser warnings of "A form element should have an id or name attribute"

[Jonathanliu92251]

When Multiselect generates html code, form elements may miss something, which cause warnings from web browser.
a quick example is, when open official website with debug mode "https://davidstutz.github.io/bootstrap-multiselect/#configuration-options-onChange", you can see browser 100+ warnings (Snapshot as below):
"A form element should have an id or name attribute" and "No label associated with a form field"

It's better to fix these warnings, thanks a lot.