fix: handle missing rel correctly

src/compiler/compile/nodes/Element.ts

@@ -620,8 +620,8 @@ export default class Element extends Node {
 
 				if (href_static_value === null || href_static_value.match(/^(https?:)?\/\//i)) {
 					const rel = attribute_map.get('rel');
-					if (rel?.is_static) {
+					if (rel == null || rel.is_static) {
-						const rel_values = rel.get_static_value().split(' ');
+						const rel_values = rel ? rel.get_static_value().split(' ') : [];
 						const expected_values = ['noreferrer'];
 						expected_values.forEach(expected_value => {
 							if (!rel || rel && rel_values.indexOf(expected_value) < 0) {