Fix soft particle rendering with engine v1.60

[slimbuck]

Editor doesn't render soft particles with engine v1.60, please make it work.

[mvaligursky]

we recently enabled color grab pass in the Editor to get dynamic refraction to work .. we need to do the same for depth grab for soft particles I think.

repro project: https://playcanvas.com/editor/scene/390137
and select individual effects in the scene view, to render them in the editor

[mvaligursky]

related to the new error when a texture is missing, added here: playcanvas/engine#4972
which skips the draw call

[willeastcott]

@mvaligursky Since the engine is now on v1.61.3, is this still an issue?

[mvaligursky]

This was fixed by @yaustar by enabling depth grab on the Editor camera.