common.inc error in newly downloaded Drupal 7.69
I think it is PHP related.  According to the Drupal 7 php requirements PHP 7.4 is not fully supported.  If you are running on 7.4 perhaps try downgrading it to 7.3 and see if it makes a difference.

This is probably the relevant issue that you encountered.  Alternatively see if you can use the latest patch in there and post your findings so you can help move the issue forward.