I belive you have misread the first line of the method. You see it's
setting AuthorInitials to aString not AuthorName. 

The complete code for the method is:

setAuthorInitials: aString

	AuthorInitials _ aString.

	"Case of being reset due to, eg, copy of image."
	aString isEmpty ifTrue: [AuthorName _ '']
	aString isEmpty ifTrue: [AuthorName _ nil]