diff --git a/lib/client-assets.php b/lib/client-assets.php
index 6b767e007648c..74aa4a7a07f3e 100644
--- a/lib/client-assets.php
+++ b/lib/client-assets.php
@@ -753,14 +753,14 @@ function gutenberg_extend_block_editor_styles_html() {
 
 	$scripts = ob_get_clean();
 
-	$editor_styles = wp_json_encode(
+	$editor_assets = wp_json_encode(
 		array(
 			'styles'  => $styles,
 			'scripts' => $scripts,
 		)
 	);
 
-	echo "<script>window.__editorAssets = $editor_styles</script>";
+	echo "<script>window.__editorAssets = $editor_assets</script>";
 }
 add_action( 'admin_footer-toplevel_page_gutenberg-edit-site', 'gutenberg_extend_block_editor_styles_html' );
 add_action( 'admin_footer-post.php', 'gutenberg_extend_block_editor_styles_html' );
diff --git a/packages/block-editor/src/components/iframe/index.js b/packages/block-editor/src/components/iframe/index.js
index c70f0915c5da9..bdf4238d35722 100644
--- a/packages/block-editor/src/components/iframe/index.js
+++ b/packages/block-editor/src/components/iframe/index.js
@@ -140,9 +140,13 @@ async function loadScript( doc, { id, src } ) {
 	return new Promise( ( resolve, reject ) => {
 		const script = doc.createElement( 'script' );
 		script.id = id;
-		script.src = src;
-		script.onload = () => resolve();
-		script.onerror = () => reject();
+		if ( src ) {
+			script.src = src;
+			script.onload = () => resolve();
+			script.onerror = () => reject();
+		} else {
+			resolve();
+		}
 		doc.head.appendChild( script );
 	} );
 }