scrollEl error / Uncaught TypeError: Cannot read property 'parentElement' of null

[santanajames]

Bug
When using scrollEl option, the console throws an error:

Uncaught TypeError: Cannot read property 'parentElement' of null

Steps to reproduce the behavior:

1. set scrollEl: {any selector}
2. refresh the page and notice console error.

Expected behavior
no console errors. stickybit should use the scroll element passed by the option

Screeshot
https://share.getcloudapp.com/9ZuEo8y8

[RomkaLTU]

Same here.