AsyncCollection.pluck returns undefined values #17

Calling .pluck('identifier') on the query below results in a collection of undefined values, even though the fields exist on the results:

await this.builder()
            .connection('default')
            .select('identifier')
            .from('migrations')
            .whereIn('identifier', identifiers)
            .get()
            .pluck<string>('identifier')

In contrast, collecting the results to a normal Collection works fine:

(await this.builder()
            .connection('default')
            .select('identifier')
            .from('migrations')
            .whereIn('identifier', identifiers)
            .get()
            .collect())
            .pluck<string>('identifier')