Simplify DTDAttributeDefinitionParser class>>#attributeDefaultValidat…

…orClassForPragma:

Fix #24

src/XML-Parser/DTDAttributeDefinitionParser.class.st

@@ -18,11 +18,10 @@ Class {
 DTDAttributeDefinitionParser class >> attributeDefaultValidatorClassForPragma: aDefaultPragma [
 	"the default pragma should have been checked for well-formedness by the
 	tokenizer so it's either empty, 'FIXED', 'REQUIRED', or 'IMPLIED'"
-	aDefaultPragma size > 0
-		ifTrue: [
-			(aDefaultPragma at: 1) == $F
+	aDefaultPragma ifNotEmpty: [
+			aDefaultPragma first == $F
 				ifTrue: [^ XMLAttributeFixedValueDefaultValidator].
-			(aDefaultPragma at: 1) == $I
+			aDefaultPragma first == $I
 				ifTrue: [^ XMLAttributeImpliedDefaultValidator].
 			^ XMLAttributeRequiredDefaultValidator].
 	^ XMLAttributeValueDefaultValidator