non-opaque objects are invisible in internal import of 0.92.0 generated pdf

Migrated from https://bugs.launchpad.net/inkscape/+bug/1656284
Checked for duplicates for open/closed issues with open+import label, launchpad with "import pdf" and "opacity pdf"

Steps to reproduce:

• open opacity0.92.0r15299.pdf in Inkscape (internal import)

What happened?

• The three purple objects on the right are invisible
• They each have a mask applied at some point (second outermost group?)
  • the mask has a group of a group of a single path
    • this path has the correct opacity, but the fill is #000000 instead of #ffffff
• internal import left, poppler import right
  • 

What should have happened?

• same output as poppler/cairo import (by appearance anyway)

Sample attachments:

• 0.92.0 r15299 export (same as in steps to reproduce) opacity0.92.0r15299.pdf
• 1.0.1 export (doesn't suffer from this issue) opacity101.pdf
• 0.92.3 export (doesn't suffer from this issue) opacity923.pdf
• original svg used for export opacity.svg

Version Info:

• 1.2-dev (f2d16dde5e, 2021-12-14) Linux Mint 20
• 1.1-dev (ad8effaa6e, 2020-11-17) Linux Mint 20
• 1.0.1 exe install Windows 10
• 0.92.3 7z archive Windows 10