Updating a Model with custom validation bug

Issue Creation Checklist

• I have read the contribution guidelines

Bug Description

When trying to Model.update() a model with custom validation, an error is thrown as the custom validator does not have access to instance fields.

SSCCE

**Here is the link to the SSCCE for this issue: https://github.com/gsqrt2/sequelize-update-validation-error

What do you expect to happen?

In regard to the SSCCE:

Connection.update( {
        approved: true
    }, {
    where: {
        approved: false
    }
})

should update Connections where approved===false to approved: true

What is actually happening?

The custom validator throws, as instance dataValues are undefined

ValidationError [SequelizeValidationError]:  Validation error: Cannot connect to self.

Additional context

The SSCCE is extremely basic, just a dummy Connection with a custom validator that ensures that the two user ids are not equal. Commenting out the validation restores normal functionality.

Environment

• Sequelize version: 6.6.5
• Node.js version: v12.19.0

Bug Report Checklist

How does this problem relate to dialects?

• I think this problem happens regardless of the dialect.
• I think this problem happens only for the following dialect(s):
• I don't know, I was using PUT-YOUR-DIALECT-HERE, with connector library version XXX and database version XXX

Would you be willing to resolve this issue by submitting a Pull Request?

• Yes, I have the time and I know how to start.
• Yes, I have the time but I don't know how to start, I would need guidance.
• No, I don't have the time, although I believe I could do it if I had the time...
• No, I don't have the time and I wouldn't even know how to start.