[Bug]: Different behavior amino_dont_omitempty x/tx

[julienrbrt]

Is there an existing issue for this?

• I have searched the existing issues

What happened?

With the bump of api in v0.52, we can see that x/tx doesn't respect the amino.dont_omitempty annotation.

For context, on main a metadata message has been added in the validator description.
It was then made nullable so that API (tagged from main) stays compatible with 0.52: #22556.
That fixed the marshal issue: https://github.com/cosmos/cosmos-sdk/actions/runs/11914721341/job/33203345359.
However x/tx has a different behavior then legacy amino when marshalling:

ref: https://github.com/cosmos/cosmos-sdk/actions/runs/12312258775/job/34363954928

Cosmos SDK Version

x/tx v1.0.0-alpha.3

How to reproduce?

No response