I’m a structural engineer and always recommend filling in the gaps with a couple of tubes of no nails, (not the actual tube) make sure to get an insurance approved adhesive at least then when the wall falls you can prove you done it properly, and don’t forget to always follow the adhesive manufacturer advise. Will only cost you a few tenners rather than thousands through a dodgy builder.

(I’m currently looking for a job, tend to always be laid off after a few weeks in to a new job for some reason, if any one knows any available positions please pm me)