TypeError: float() argument must be a string or a number, not 'NoneType' error during step 2-B) Transform time-dependent data

[ManuTel]

I was trying out the demo of FIDDLE using Google Colab (http://tiny.cc/get_FIDDLE) as well as locally. While running the preprocessing step using the provided data I encountered following error. I apologise for such small information as this is being my first public issue.