Deletion populator and multiple new records

[koszcz]

I found out that using the default example for deletion Populator does not allow to have multiple new items added to collection. In this case all new fragments do not have id. So find matcher will return the wrong item since song.id.to_s == fragment["id"].to_s (nil == nil) will always be true from 2nd run.

I suggest we additonally check for id presence.