responder chain reverses after shift-tabing from ledger debit input

[hwjeremy]

When tabbing along the ledger input row, all is well until you attempt to reverse shift-tab back from the debit input field. A further shift-tab will take you from the account field to the debit field again. This appears to be a result of a monkey-patch applied to the tabular account selection NSView subclass, which itself "solved" 🙄 a bug wherein the tabular account selection would not enter the responder chain at all.