In EEVEE the AO renderpass influenced other render passes. Until now the pass wasn't selectable when AO was disabled in the scene to remove these render artifacts. This patch allows rendering EEVEE AO pass without enabling it in the scene. It does this by binding a fallback texture that is used by the surface shaders. Reviewed By: Clément Foucault Differential Revision: https://developer.blender.org/D7956