core: attribute selectors with comma not working

[igorbt]

When using nested attribute selectors that contains commas, they generate incorrect styles, inserting ampersands after the comma.

For example:

    '& [style*="color: rgb(245, 240, 241);"]': {
      color: 'black !important'
    },

will result in something like

.fk7b603 [style*="color: rgb(245,& 240,& 241);"] { color: black !important; }

See more in this Codesandbox.