Resolve "USAN: applying zero offset to null pointer in lib_rend/ivas_objectRenderer_fx.c:426:9"

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• Requested reviewers:

Reason why this change is needed

• USAN error triggered by clang 18 sanitizer

Description of the change

• avoid indexing into Quaternions and Pos pointers when they are NULL

Affected operating points

• Renderer only, should be BE in most cases, but in general undefined behaviour possible

Closes #2458 (closed)