Fix processLineAgainstMesh crashes when checking for colored meshes

[Xenius97]

Summary

Fixed crash in processLineAgainstMesh when processing models with colored meshes (no texture coordinates). The function now safely handles models without UV data by using barycentric coordinates as a fallback.
Fixes: #4632

Motivation

The function would crash with an access violation (0xC0000005) when called on certain models that only have vertex colors without texture coordinates (e.g., model IDs: 13656, 13606, 3081, 3060, 1784, 2070, 2077, 2122, 2742, 2772, 8146, 953, 1318, 2594, 2782, 2602, 2781).

Test plan

• Models with textures: Returns correct UV coordinates and texture names (existing behavior preserved)
• Models without textures (colored mesh only): Returns barycentric coordinates as UV
• Problematic model IDs from crash report (2781, 2782, etc.): All now work correctly

Test script: The attached resource spawns a test object at (0, 0, 3). You can change the model ID at the beginning of the script. (Shader won't apply on these object, thats a different issue)
process_test.zip

gta_sa_3erIIBjOun.mp4

Checklist

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