Can't filter by null values on JSONB fields

[benedyktdryl]

Bug description

Can't filter by null values on JSONB fields

How to reproduce

1. Run query with null value filter

prisma.model.findMany({
  where: {
    NOT: {
      data: {
        path: ["foo"],
        equals: null,
      },
    },
  },
});

2. See error:

Argument equals for where.NOT.0.data.equals must not be null. Please use undefined instead.

Expected behavior

As JSONB values are allowed, I should be able to find values filtered by null.

Prisma information

model model {
  id               String            @id @db.Uuid
  data             Json
}

Environment & setup

• OS: MacOS
• Database: PostgreSQL
• Node.js version: 14.x

Prisma Version

`"@prisma/client": "^2.20.1"`