Sync Server Fuzzer found inconsistency applying empty binary/string to mixed list

[sync-by-unito]

The fuzzer captured this failure. I reproduced it to this minimal test case.

Apply these instructions:

AddTable { table: gr, tableType: Top-Level, pkName: _id, pkType: String, pkNullable: false }
AddColumn { table: gr, field: vg, type: Mixed, collection: List, isNullable: true, targetTable:  }
CreateObject { table: "gr", id: "{String: "cavhdqmgvna"}" }
ArrayInsert { (table="gr", ID="{String: "cavhdqmgvna"}", fullPath="vg.0"), payload: {Binary: Binary(string: , raw: [])}, priorSize: 0 }
Update { (table="gr", ID="{String: "cavhdqmgvna"}", fullPath="vg.0"), payload: {String: ""}, isDefault: false, priorSize: 1 }

And the result of the object will be:

{
"class_gr":[{"_id":"cavhdqmgvna","vg":[{"$binary": {"base64": "", "subType": "00"}}]}]
}

As you can see, setting a mixed list to just be a single element with an empty binary payload and then updating it to be an empty string winds up resulting in the list still just being an empty binary.

I updated the binaries we are using to the most recent master release for realm-core.

This reminds me of this ticket and I would bet its related in some way: https://jira.mongodb.org/browse/RCORE-802