System Information
Operating system: Windows 11
Graphics card: nVidia RTX 3060

Blender Version
Broken: 3.3.0, 3.2.1

Short description of error
When saving an image of an emission volume with a transparent background, Blender renders the image properly, but appears to save out an image of nothing.

Exact steps for others to reproduce the error
From default startup: In the material of the default cube, remove the principled shader and add an emission shader connected to the volume input of the material output. Then, in either EEVEE or Cycles settings (both share this problem) turn on background transparency in the render properties under film. Render an image and save it out as a png file with RGBA enabled. The file when viewed in other software and even in Blender's own image editor will appear to be blank, though the image WILL appear in Blender's compositor via an image node. So the image works, just not as a user may expect it to or find useful.

Sorry if this is expected behavior.