Route AJAX failure messages to console instead of popup
You can check Prevent JS alerts module..

Project page says


  This module is an answer to the issue: #1232416: Drupal alerts "An
  AJAX HTTP request terminated abnormally" during normal site operation,
  confusing site visitors/editors, which describes a big problem for end
  users: JavaScript alert();'s for end users on AJAX errors by Drupal
  core. Perhaps it will one day become obsolete, when this bug is fixed.
  End users are often frightened of these errors and don't know, if they
  have "destroyed the internet" ;)
  
  This module completely suppresses ALL JavaScript alerts and instead
  prints them to console via console.error! Important: It does NOT ONLY
  suppress the core alerts, but also custom alerts.