Storm shader compile error with a primvar reader connected to opacity

[marktucker]

Description of Issue

Usdview rendering with Storm outputs a shader compiler error when loading an asset with a USD Preview Surface material with a Primvar Reader prim connected to the opacity input of the material. This seems to be a regression as the same material works in USD 21.11, but produces an error in USD 22.05.

Steps to Reproduce

1. Open the attached asset in usdview 22.05:
   torus.zip
2. Error is printed to terminal, and the material doesn't display properly (the torus should be green). The error message looks like:

Error in 'pxrInternal_v0_22__pxrReserved__::HdSt_DrawBatch::_GetDrawingP
rogram' at line 279 in file F:\dev_tools\src\usd\usd-22.05\USD-py3.9\pxr\imaging
\hdSt\drawBatch.cpp : 'Failed to compile shader for prim /torus1/mesh_0.'

Package Versions

22.05

[jilliene]

Filed as internal issue #USD-7374