System Information
Operating system: Windows-10-10.0.17134 64 Bits
Graphics card: GeForce GTX TITAN X/PCIe/SSE2 NVIDIA Corporation 4.5.0 NVIDIA 430.86

Blender Version
Broken: version: 2.80 (sub 74), branch: master, commit date: 2019-06-19 18:29, hash: rBd30f72dfd8ac
Worked: (optional)

Short description of error
Cycles - Volume rendering fails with Principle Volume Shader, when Film Transparent is on

Exact steps for others to reproduce the error

Open the attached blend file.

Click render Image (F12). Nothing is rendered.
Switch Transparent off, in the render settings.
Render Image again. The volumes are shown but with grey background.
So no compositing of volumes is possible, because they can´t be rendered without the background.
The problem is only with the Principle Volume Shader, if you use the old Volume Scatter shader rendering with transparent background works!
Viewport rendering works, only when you use Render Image or Render Animation the volume isn´t rendered with the principle volume shader and film transparent on.