Unable to unbind START button in controller config

First and foremost consider this:

• Only RetroArch bugs should be filed here. Not core bugs or game bugs
• This is not a forum or a help section, this is strictly developer oriented

Description

Hello. In my joystick for some reason the X button has same code as START button - 100. I need to unbind START button so pressing X does not generat pressing START button. Unbinding START button is not possible. In cfg file all start buttons have configuration "null", yet in the configuration of console START shows 100. There is not other config file which I could modify. I cannot use keyboard - Android does not show virtual keyboard when configuring controller input.

Expected behavior

START button should be unbound by pressing some joystick key, preferrably by START button.

Actual behavior

Steps to reproduce the bug

1. Go to user config
2. Find START button
3. Try to completely unbind (I can still use on-screen START)

Bisect Results

[Try to bisect and tell us when this started happening]

Version/Commit

You can find this information under Information/System Information

• RetroArch: Latest Android

Environment information

• OS: Android
• Compiler: [In case you are running local builds]

Reproduce the controller configuration flow on Android using the reported duplicate button code and verify how START is represented when its configuration is set to null. Done means a user can completely unbind START through the joystick configuration, while the on-screen START control remains usable; the issue does not name a file or test to start from.