In the dialog of lesson 17.0, “Preparing a Party," Eric says:
Je pensais que l’on pourrais faire la fête dans le jardin et inviter tous ses amis et la famille.
Everything makes sense to me except for one thing: why did he say “que l'on pourrais"? I would have said “que on pourrais." What does “le” or “la” refer to here? Is it Isabelle, his sweetheart for whom he is preparing the party? And if so, as an indirect object, why would he not use “lui”? Or does can “lui” be contracted to “l'”?
I am just starting with Rocket French with Level 3, so maybe this was covered in an earlier lesson that I missed and you could point me to.