Disabled styling doesn't always work

[yh54321]

When the disabled attribute is set to true on the checkbox, both the checkbox and its associated label are correctly disabled and adopt a 'disabled' styling (they become grayed, and mouse pointer changes).

When the checkbox exists in a <fieldset> element and the fieldset's disabled attribute is set to true, the checkbox becomes functionally disabled, though it does not adopt a 'disabled' styling.

If I am not mistaken, the expected behavior is for the checkbox and its label to likewise adopt a disabled styling under this circumstance.

[helptiger]

It seems that it is related to this
jgthms/bulma#2271