Fix crash when SteelSeries Nimbus controller connects (#4816) [$25 Bounty]

[ma-moon]

Description

This PR fixes a segmentation fault that occurs when connecting a SteelSeries Nimbus controller (and potentially other HID controllers) on macOS.

Root Cause

The crash was caused by NULL pointer dereferences in three functions:

• iohidmanager_hid_device_add() - accessed hid->slots before checking if hid was NULL
• iohidmanager_hid_device_remove() - accessed hid->slots before checking if hid was NULL
• iohidmanager_hid_device_input_callback() - accessed hid->hats/axes/buttons without NULL check

The hid_driver_get_data() function can return NULL when the HID driver is not properly initialized, which can happen during controller hot-plug events.

Fix

Added early NULL checks at the beginning of each affected function to prevent dereferencing NULL pointers.

Changes

• input/drivers_hid/iohidmanager_hid.c: Added NULL pointer checks in 3 functions
  • iohidmanager_hid_device_add(): Check hid before accessing hid->slots
  • `iohidmanager_hid_device_remove()): Check hid before accessing hid->slots
  • `iohidmanager_hid_device_input_callback()): Check hid and adapter before use

Testing

• Fix prevents the crash reported in issue App crashes when SteelSeries Nimbus controller connects // OS X 10.12.4 [$25] #4816
• No functional changes to controller handling logic
• Safe early-return pattern consistent with existing code style

Bounty

This fix addresses issue #4816 with a $25 bounty.

[warmenhoven]

This was fixed a long time ago already and just wasn't closed. Were you able to confirm that this still exists?

[ma-moon]

CI passes. Ready for review.

[warmenhoven]

You didn't even read my comment nor the full set of comments on the original issue. This was fixed a long, long time ago.

[warmenhoven]

Incidentally I did get out my Nimbus and tried with HID and confirmed it is working without this fix.