I don’t see anything on line 419 in the latest version of ACF that could cause that error. What version of ACF are you using? What is on line 419 of that that file in your version?
Try updating ACF to the latest version.
Any idea what code in your theme is triggering the error?
https://wordpress.org/support/article/debugging-in-wordpress/
Turn on debug display, load a page on you site where the error happens, find the code in your template files that corresponds to the location on the page where the error is shown.
