FIX: Added checks to prevent NullReferenceException (#2364)

Co-authored-by: Sam Yu <sam.yu@sam.yu-70VM>
Co-authored-by: João Freire <joao.freire@unity3d.com>

Author: 3 people

Packages/com.unity.inputsystem/CHANGELOG.md

@@ -9,6 +9,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
 
 ### Fixed
 
+- Fixed a `NullPointerReferenceException` thrown in `InputManagerStateMonitors.FireStateChangeNotifications` logging by adding validation [UUM-136095].
 - Fixed auto-save not working for Input System actions in Project Settings when both the Project Settings and Input System Actions windows were open [UUM-134035](https://jira.unity3d.com/browse/UUM-134035)
 - Improved New Input System warning dialog, Native Device Inputs Not Enabled [UUM-132151].
 - Fixed caching for InputControlPath display name [ISX-2501](https://jira.unity3d.com/browse/ISX-2501)

Packages/com.unity.inputsystem/InputSystem/InputManagerStateMonitors.cs

@@ -397,7 +397,7 @@ internal unsafe void FireStateChangeNotifications(int deviceIndex, double intern
                 catch (Exception exception)
                 {
                     Debug.LogError(
-                        $"Exception '{exception.GetType().Name}' thrown from state change monitor '{listener.monitor.GetType().Name}' on '{listener.control}'");
+                        $"Exception '{exception.GetType().Name}' thrown from state change monitor '{(listener.monitor?.GetType().Name ?? "null")}' on '{(listener.control?.ToString() ?? "null")}'");
                     Debug.LogException(exception);
                 }