Ignore blank lines in *.txt labels

[glenn-jocher]

Fix for #958 (comment)

🛠️ PR Summary

_{Made with ❤️ by Ultralytics Actions}

🌟 Summary

Enhanced label parsing in dataset utility to ignore empty lines.

📊 Key Changes

• Updated label reading logic to skip empty lines when parsing label files.

🎯 Purpose & Impact

• Purpose: Prevents potential errors or misinterpretations of label files with unintended empty lines.
• Impact: Improves the robustness of dataset preparation by ensuring that label parsing is more fault-tolerant, leading to a smoother training process for YOLOv5 models. Users can expect more reliable data preprocessing, especially in cases where label files might have contained superfluous empty lines. 🛠️