Error during analysis: 'NoneType' object has no attribute 'lower

[guinslym]

Sometimes I am getting this error while running the script

Error during analysis: 'NoneType' object has no attribute 'lower'""" on the line ```

Generate Advanced time analysis visualization

    analyzer.create_advanced_time_analysis()

sometimes I rerun the code and everything works. 

What I did is that I commented `        # Generate individual visualization files
        analyzer.save_individual_visualizations()
        
        # Generate time analysis visualization
        analyzer.create_time_analysis()

        # Generate Advanced time analysis visualization
        analyzer.create_advanced_time_analysis()

        # Add operator location analysis
        analyzer.analyze_operator_location()`


Than run the code. Then uncommented them and run the code.