fix exception with empty alt attribute (#4778)

Author: Conduitry

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Svelte changelog
 
+## Unreleased
+
+* Fix compiler exception with `a11y-img-redundant-alt` and value-less `alt` attribute ([#4777](https://github.com/sveltejs/svelte/issues/4777))
+
 ## 3.22.1
 
 * Fix compiler exception with `a11y-img-redundant-alt` and dynamic `alt` attribute ([#4770](https://github.com/sveltejs/svelte/issues/4770))

src/compiler/compile/nodes/Element.ts

@@ -488,7 +488,7 @@ export default class Element extends Node {
 			if (alt_attribute && !aria_hidden_exist) {
 				const alt_value = alt_attribute.get_static_value();
 
-				if (alt_value && alt_value.match(/\b(image|picture|photo)\b/i)) {
+				if (/\b(image|picture|photo)\b/i.test(alt_value)) {
 					component.warn(this, {
 						code: `a11y-img-redundant-alt`,
 						message: `A11y: Screenreaders already announce <img> elements as an image.`

test/validator/samples/a11y-img-redundant-alt/input.svelte

@@ -6,3 +6,4 @@
 <img src="bar" alt="Plant doing photosynthesis in the afternoon" />
 <img src="foo" alt="Picturesque food" />
 <img src="baz" alt={'baz'} />
+<img src="baz" alt />