Fix min-mass update when adding decay products

This is extracted from 50a1f8f5, and is needed for working closure tests between 10-rewrite-settings-input and master, when Hadron Decays are enabled. Otherwise some events will occasionally have different hadron decay chains, which will eventually lead to differing statistics and results.

I don't know about the structure of HADRONS++, so if you say the change is actually incorrect, I'll instead update the 10-rewrite-settings-input branch and we can close the MR.