Background color in splatfacto renders can be random if no crop is set

[kerrj]

Describe the bug When rendering splatfacto, if a crop isn't set the background color will be random

To Reproduce Steps to reproduce the behavior: ns-render any splatfacto model where the background is poorly defined (ie underreconstructed)

Expected behavior same color as viewer will be in background

Screenshots See orange in background of this scene

Additional context in render.py, BACKGROUND_COLOR_OVERRIDE is only set if the crop is set, this should be set whether the crop is used or not.