Fix negative balance on ETH.
Fix negative balance on ETH.

That bug was due to how operations got sorted after internal
transactions were taken into account. Descending-sorting them would
“work” in some cases (aka. we got very (badly?!) lucky on our
integration tests not to fall into this pitfall.

I detected that problem by looking at cumulative balance histories while
doing some lldb session. Even though the date were correctly ascending,
the operations were decreasing in a very weird order.

One-byte change, ladies and gent.

LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core,LedgerHQ/lib-ledger-core