We must ensure there's space for the terminating null in the temporary buffer in `imgact_binmisc_populate_interp()`.
Note that there is not a possible buffer overflow here, because `xbe->xbe_interpreter`'s length and null termination is checked in `imgact_binmisc_add_entry()` before `imgact_binmisc_populate_interp()` is called, but the latter should correctly enforce its own bounds.