Fix Phantom Input From Disabling an Input Device

Description

When a controller is plugged in and the user changes the player 1 device index to 'Disabled', the screen will constantly scroll upwards, accelerating as though the user is holding the up direction, until Retroarch is restarted and the device index is changed either through the menu or a config file edit.

It is very easy to inadvertantly disable an input device while cycling through the device options, leading to this issue.

Expected behavior

When an input device used to control is disabled then it should be disabled, and all input "gathered" from it should be ignored.

Actual behavior

When an input device used to control is disabled, it seems to hold onto a phantom input, scrolling the selection upwards, rendering the program near-unusable until a restart.

Steps to reproduce the bug

1. Plug in a controller
2. Navigate to Player 1 controls
3. Change the device index to 'Disabled'

Bisect Results

This occurs as far back as stable 1.7.5, but with one nuance: changing the device index from the default, 'Xinput Controller', to the unconfigured 'Hori Mini Wired Gamepad' results in the same permenant scrolling upwards, and setting it to 'Disabled' removes the phantom input.

Version/Commit

• RetroArch: 1.8.9

Environment information

• OS: Windows 10, latest mandatory updates as July 28, 2020.

Reproduce the issue with a controller by changing the Player 1 device index to Disabled, then trace RetroArch's input handling for disabled devices. Done means input gathered from the disabled device is ignored, selection no longer scrolls upward, and no restart is needed.