Error on delete income

[ririko5834]

When tried to delete income entry got error

Also got error when tried to delete those default categories

[ririko5834]

When deleted income directly from db now getting this error

[ririko5834]

Tried to add incomes back but it still does not work

[ririko5834]

It isnt possible to have minus balance? I want to use it to track debts (when someone borrow money from me, I want to track it)