[*] MO: blockcart animation optimization

THIS IS WRONG - I NEED TO MERGE INTO DEVELOPMENT BRANCH. WILL TRY TO EDIT BUT I'M NEW TO GITHUB...!

The animated element would not be removed upon the animation being finished. This would make the site slow and unresponsive if the animated image was heavy (eg. a transparent png) and added many times without reloading. This fix makes the animation behave as expected also when performing it multiple times.