title: "Balances: add failsafe for consumer ref underflow"

doc:
  - audience: Runtime Dev
    description: |
      Pallet balances now handles the case that historic accounts violate a invariant that they should have a consumer ref on `reserved > 0` balance.  
      This disallows such accounts from reaping and should prevent TI from getting messed up even more.

crates:
  - name: pallet-balances
    bump: patch