Unless you're manually injecting 0x08 into a database record, isn't it your keyboard that interprets your backspace into the UI layer. There's no way to type a backspace without literally pressing backspace :)
Regarding the null, if it's C based, theoretically your password just stops there. All other chars after that would be ignored.
Now I wonder, what would other non-C languages do if they see 0x00 in a string?