When I try to open a realm with sync enabled using a partition value of "" (empty string), I get the following error: "partitionValue of type 'string' may not be an empty string". It looks like this was added in https://github.com/realm/realm-js/pull/3205. The sync server does not impose this restriction so I don't think this check should be enforced by the client.

The check which leads to the exception is https://github.com/realm/realm-js/blob/master/src/js_sync.hpp#L66-L68