Creating user menu items with icon URL's causes misaligned menu item

Following docs on using User menu items with URL to point to a file elsewhere - https://docs.moodle.org/33/en/Theme_settings#User_menu_items

For the purpose of this issue, I've just used the URL of an icon in the root pix folder (in real usage we are using the URL of an icon in one of our plugins, i.e. "/theme/image.php/clean/local_foo/0/icon")

I've added the following User menu items as follows:

courses,moodle|course/index.php|/pix/help.png

See attached screenshots from Clean & Boost themes showing misalignment:

Clean	Boost