HTML Widget: toggleClass() should be passed true/false as second param

[iCaleb]

​http://api.jquery.com/toggleclass/

It expects either true or false for the second parameter, passing an integer will just toggle on/off which is sometimes not the desired result.

Found the problem here: ​https://github.com/WordPress/WordPress/blob/4.9-branch/wp-admin/js/widgets/custom-html-widgets.js#L207, with correct usage found here: ​https://github.com/WordPress/WordPress/blob/4.9-branch/wp-admin/js/theme-plugin-editor.js#L365

Replying to iCaleb:

It expects either true or false for the second parameter, passing an integer will just toggle on/off which is sometimes not the desired result.

Confirmed, toggleClass( ..., 0 ) is not the same as toggleClass( ..., false ), and just acts as a regular toggle. Likewise, toggleClass( ..., 1 ) is not the same as toggleClass( ..., true ).

In 42457:

Widgets: When checking for errors in Custom HTML widget, pass correct value to toggleClass() for Save button.

toggleClass() expects a boolean as a second argument, not an integer.

Props iCaleb.
Fixes #42867.

In 42458:

Widgets: When checking for errors in Custom HTML widget, pass correct value to toggleClass() for Save button.

toggleClass() expects a boolean as a second argument, not an integer.

Props iCaleb.
Merges 42457 to the 4.9 branch.
Fixes #42867.