How to reproduce:
1. Create a new LWRP project and create a new Scene
2. Go to "Edit" -> "Project Settings..." -> "Graphics" and set the Render pipeline asset to "None" under the "Scriptable Render Pipeline Settings" setting
3. Create a new terrain, add a grass texture and try to paint onto the terrain
4. Observe the terrain in the Scene View

Expected result: The grass textures are drawn successfully
Actual result: Trying to paint the grass textures fails without any errors, the textures simply don't appear onto the terrain

Reproduced in: 2019.1.0a10, 2018.3.0b12, 2018.2.18f1, 2018.1.9f2

Note: The bug does not occur with the HDRP package