get_bucket_df crashes when S3 Object only has 'Owner' 'ID' (missing 'DisplayName')

[lorenzgerber]

get_bucket_df() crashes when the accessed S3 object has e.g. only 'ID' in 'Owner' (no/missing 'DisplayName', which is allowed according AWS API ).

In such a case, the list level 'ID' get's "flattened" away, and the data appears as 'Owner'. This will crash the as.data.frame.s3_bucket function which expects [["Owner"]][["ID"]] and [["Owner"]][["DisplayName"]] to exist.