Vaccum/mop function

I mop and vac my house everyday... well my dreame L50 does...

Issue is my water tank needs water every 2nd day...

I have set it on the vac then mop so it can vaccum and if there is no water skip the mopping but mop when there is.

Issue is, when it doesn't have water, it won't even vaccum...

How can I resolve this? It must vaccum and mop when water is there but if there is no water it still needs to vaccum.

What happens when you set it to vacuum and mop after?