Fix error from adding blank target to external links (#2575)

## Motivation for the change, related issues

We use playground as a preview tool inside an app that generates
WordPress blocks via AI assistant. We encounter `JavaScript Error:
TypeError: e.target.closest is not a function` coming from Playground
and it encumbers our assisted error recovery because it comes from
outside of the generated code.

## Implementation details

We don't attempt to update the link if the element surprisingly doesn't
have a closest method (which is why we also log the element to see why
this happens)

## Testing Instructions (or ideally a Blueprint)

Hard to figure out, sometimes it occurs.

---------

Co-authored-by: Adam Zieliński <[email protected]>

Author: draganescu

packages/playground/remote/src/lib/playground-mu-plugin/0-playground.php

@@ -100,7 +100,7 @@ function playground_add_target_blank_to_external_links() {
 	if (empty($_SERVER['REQUEST_URI']) || wp_doing_ajax() || wp_doing_cron()) {
 		return;
 	}
-	
+
 	?>
 	<script>
 		function addTargetBlankToExternalLinks() {
@@ -116,18 +116,26 @@ function addTargetBlank(a) {
 			document.querySelectorAll('a[href]').forEach(a => {
 				addTargetBlank(a);
 			});
-			
+
 			// Set target="_blank" for external links when clicked.
 			// This covers links that are added after the page has loaded.
 			document.addEventListener('click', e => {
-				const a = e.target?.closest('a[href]');
+				// window, document, SVG Text nodes etc. don't have the `closest` method
+				if ( !e.target?.closest ) {
+					return;
+				}
+				const a = e.target.closest('a[href]');
 				if (!a) return;
 				addTargetBlank(a);
 			});
 
 			// Also handle focus events to cover keyboard navigation on
 			// links that are added after the page has loaded.
 			document.addEventListener('focus', e => {
+				// window, document, SVG Text nodes etc. don't have the `closest` method
+				if ( !e.target?.closest ) {
+					return;
+				}
 				const a = e.target?.closest('a[href]');
 				if (!a) return;
 				addTargetBlank(a);