[Woo POS] Multiple readers found can be shown empty

[joshheald]

https://github.com/user-attachments/assets/1e5c0721-8796-40f2-b01e-a44c7234e5a8

Note that this video shows an issue at the end where the Multiple Readers View is shown empty after tapping try again on the error. That's an underlying bug, and out of the scope to fix here, but I'll raise an issue. Found in #13775

The multiple readers alert should not show empty... unless it becomes empty while on screen.

If it's showing, it should continue searching.

In this case, it's probably ignoring the two previously found readers.