Leaving overtime field blank when adding a new officer causes an error

[brianmwaters]

When adding an officer using the form at https://openoversight.com/officer/new, if the "OVERTIME PAY" field is left blank, then after the form is submitted, the user sees an error that reads "Not a valid decimal value" (see screenshot).

The desired behavior should be, that if the OT field is left blank, then the app assumes that OT pay was $0 or unknown, and proceeds without error.