Audio Remove step sound from FPSController

Hi! Unity newbie here. I'm using the FPSController, and I'm trying to get rid of the step sounds. I've tried setting the Footsteps Sound Size to 0, which results in the following error message:

IndexOutOfRangeException: Array index is out of range.
UnityStandardAssets.Characters.FirstPerson.FirstPersonController.PlayFootStepAudio () (at Assets/Standard Assets/Characters/FirstPersonCharacter/Scripts/FirstPersonController.cs:172)
UnityStandardAssets.Characters.FirstPerson.FirstPersonController.ProgressStepCycle (Single speed) (at Assets/Standard Assets/Characters/FirstPersonCharacter/Scripts/FirstPersonController.cs:159)
UnityStandardAssets.Characters.FirstPerson.FirstPersonController.FixedUpdate () (at Assets/Standard Assets/Characters/FirstPersonCharacter/Scripts/FirstPersonController.cs:130)

I've also tried removing the audio file used for the steps, but that makes my background sound (audio source on the FPS) go silent.

I haven't been able to find another FPS without steps. What I need it for is to walk around at ground level and have a collider that interacts with other object.

Suggestions would be very appreciated!