Why does the error pop up and how to optimize the code?

Question

JavaScript

Good afternoon.
There are 2 scripts, one is responsible for the opacity of the blocks when scrolling, the second is for filling the statusbars one by one in the same blocks.
How to merge them so that the status bars start to work simultaneously with the removal of opasity from the blocks?
And another question: the console throws Uncaught TypeError: Cannot read property 'offsetHeight' of undefined - but everything works. How to fix it?
Still not strong in JS(((
Thanks for the help.

https://codepen.io/aliakseibarsukov/pen/oNWxqaV