val.py assert ncm == nc fix

[glenn-jocher]

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhanced error message for model and dataset class mismatch in validation script.

📊 Key Changes

• Modified the assertion error message in val.py to display the complete weights array when a class mismatch is detected.

🎯 Purpose & Impact

• Purpose: To provide a more informative error message to users when their model's number of classes doesn't match the dataset classes during validation.
• Impact: This change will help users quickly identify issues when using datasets with a different number of classes than the model was trained on, improving debugging and user experience. ⚙️🔍