Materials turn into Hidden/InternalErrorShader after conversion

[shino-a]

Describe the bug
Materials change to Hidden/InternalErrorShader after being processed by the Shader Converter.

To Reproduce
Steps to reproduce the behavior:

1. Create a material using the shader you wish to convert, then save the project.
2. Open the Unity Toon Shader Converter via Window > Rendering > Unity Toon Shader Converter.
3. Select the RenderPipelineConverterContainer corresponding to the shader from Step 1, and click the "Scan the project" button.
4. Verify that the material created in Step 1 is in the list, then click "Convert Materials."
5. The material's shader incorrectly changes to Hidden/InternalErrorShader.

Expected behavior
The material's shader should be correctly converted to Toon/Toon or Toon/Toon (Tessellation).

Additional context

• This issue occurs in version 0.13.0-preview and later.
• It is caused by the shader name changes introduced in refactor: put "Toon" prefix for Toon shaders  #655 .
• There may be similar issues in other places where shader names are referenced (not yet tested).

[sindharta-tanuwijaya]

Thanks for the clear report and for identifying the likely regression point.