GitLab

Fixes: #33212

Upstream PR: https://github.com/ulfalizer/Kconfiglib/pull/103

Ignoring when user inputs NULL in a text field.
menuconfig exits with a python stack trace if NULL is provided as input
character, therefore ignore NULL as an input character to prevent this
behaviour.

A NULL character may be given accidentally by the user through the
following ways:
- Pressing `Win` key on keyboard (Windows only)
- Pressing `<CTRL>-@` / `<CTRL>-2`.
Signed-off-by: Torsten Rasmussen <Torsten.Rasmussen@nordicsemi.no>