Default values for new properties

Im using ObjectBox in a pet android project written in Kotlin.. I have a data class encoded as such (example):

@Entity data class Foo(var name:String, var description: String) {
    constructor() : this("", "") // parameter-less constructor
    @Id var id: Long = 0L
    // other stuff
}

Database already existed on the device.. I added an additional property to the Foo class (not in the data constructor):

@Entity data class Foo(var name:String, var description: String) {
    constructor() : this("", "") // parameter-less constructor
    @Id var id: Long = 0L
    var bar: String = ""
    // other stuff
}

defaulted, non-null object bar.. however when pulling existing records from the stored box, that value bar appears to be null.. I would expect it to be a blank string (default for the parameter); is the violation of not-null guarantee coming from the Java interop?

I fixed the issue by nuking the database; afterwords the entity created and stored is not-null.. But this brings up any possible future updates that may violate this.

Is there a "database upgrade" method for updating already stored objects between versions, adding default values to new properties, or am I resigned to make anything added to an existing model be nullable (and handle it as such)?

The issue provides a Kotlin Foo entity and describes existing records in an ObjectBox database, but names no repository files or tests. Start by reproducing the behavior after adding bar to Foo, then inspect the entity migration and existing-record loading paths. Done means establishing how new non-null properties receive defaults for stored records, with coverage or documentation for future upgrades.