Restrict access add 2 grade conditions button with empty label

Issue
Form labels - Inappropriate use of label on the add 2 grade conditions to forum button (considered an orphan label) in the restrict access filed set.

Standard Level
WCAG 2 1.1.1 (A) http://www.w3.org/WAI/WCAG20/quickref/#qr-text-equiv-all

Impact
Serious

Example Link
http://demo.moodle.net/course/modedit.php?add=assign&type=&course=625&section=2&return=0&sr=0

Test Steps

1. Login as teacher
2. Navigate to CF101
3. Click add activity or resource link
4. Select assignment
5. View the source code for the add 2 grade conditions to form button.