Skip trueup check if previous_user_count is absent

What does this MR do and why?

Skip trueup check if previous_user_count is absent

How to set up and validate locally

I've recreated the original scenario, but it's a bit hard to do so elsewhere, so I've made the recording to show the before and after.

(sorry about the keyboard sound, I didn't setup the mic properly).

https://youtu.be/V3KOnVISNVs (on GitLab Unfiltered)

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.

Related to #361345