string.matches throws error when we pass a string as second parameter

Describe the bug In 0.28.1, these 2 signatures work:

• string.matches(regex: Regex, message?: string | function): Schema
• string.matches(regex: Regex, options: { message: string, excludeEmptyString: bool }): Schema

In 0.28.2: The first one throws an error. Cannot use 'in' operator to search for 'excludeEmptyString' in <message>

The bug has been introduced here: https://github.com/jquense/yup/commit/27e5d684acb7563fa44c4da6baa8e81c94a08c34#diff-57c5960218f1091895b3610a7d779378R79

If options is a string, we cannot make this operation 'excludeEmptyString' in options.

To Reproduce

const schema = yup.string().matches(/test/, 'My message')
await schema.isValid('hi')

Expected behavior Should not throw an error

[gellati]

I also had this error. The function expects an object, but a string is passed to it and therefore an error message is given. A rollback fixed the issue also for me, but I also made this pull request #801 for a suggested fix.

[kris2kris]

Same problem for me, rollback in 0.28.1 solve the problem