fix: crash by illegal memory access

[devgdovg]

Motivation

Fix issue: #773

Modifications

add dummy comfy_cast_weights and weight fields for SVDQW4A4Linear module to make it compatible with low vram offloading in ComfyUI

Checklist

• Code is formatted using Pre-Commit hooks (run pre-commit run --all-files).
• Relevant unit tests are added in the tests/workflows directory following the guidance in the Contribution Guide.
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• Additional custom nodes (if needed) are added to .github/workflows/pr-test.yaml.
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[lmxyy]

Passed tests.