AIO my partner has their ex as their emergency contact

We've been together about 9 months. I accidentally saw a document and I (shamefully) kept reading it because it was sitting there. Most of it was normal stuff, but I noticed that my partner's ex was listed as their emergency contact and beneficiary in the event something horrible happens. Tbf they had been together for 6-7 years previously (never married), but they've been broken up for a few years.

I have kept this to myself, but I felt my stomach sink a little when I read it. It's made me feel like there's a tiny cannon ball in my stomach physically (and in my heart emotionally). It's weighing me down.

It's possible my partner has just forgot that they set things up that way. I don't have experience with being in contact with, or giving much thought to, an ex. I haven't had that many, and those who were in my past I moved on from and feel neutral towards, and they're in no way a part of my life. Because this is my experience, my immediate response is: my partner must still have strong feelings for their ex. Even the thought of strong platonic feelings, of my partner caring for them like a friend/family member, makes me uncomfortable, which may be a problem on my part.

I need to bring it up and talk about it (I know communication is key), but I want to calm my emotions down first because I still feel hurt for some reason. Even though it may be a perfectly normal situation. Am I overreacting? Is it odd? I just want some neutral feedback from strangers rn.