I'm having the same issue:
"Fatal error: Allowed memory size of 268435456 bytes exhausted (tried to allocate 26020 bytes) in /Applications/XAMPP/xamppfiles/htdocs/sites/abm-sites/granite-shop/webassist/file_manipulation/helperphp.php on line 1146"
Historically, I've just added the ini_set memory limit and it's been fine... However I have this as the first line on both pages I'm getting this error on:
"<?php ini_set("memory_limit", "256M") ?>"
What's equally odd, historically I've run into this on the live server, but not locally in XAMPP. I'm getting the error on both, even when trying to upload images less than 1 MB.