Line 2687 reads:

$category->name = get_string('uncategorised', 'grades');

which uses the string 'uncategorised'

where as lines 2115 and 2390 use the defined variable UNCATEGORISED

I think we should be consistent and would recommend changing line 2687 to:

$category->name = get_string(UNCATEGORISED, 'grades'); (this is what Jeff has in GBPv2 but it is different in CVS for 18STABLE.