Fix check for selectedBlockToolsRef

packages/block-editor/src/components/block-tools/index.js

@@ -137,7 +137,7 @@ export default function BlockTools( {
 				insertBeforeBlock( clientIds[ 0 ] );
 			}
 		} else if ( isMatch( 'core/block-editor/unselect', event ) ) {
-			if ( selectedBlockToolsRef.current.contains( event.target ) ) {
+			if ( selectedBlockToolsRef?.current?.contains( event.target ) ) {
 				// This shouldn't be necessary, but we have a combination of a few things all combining to create a situation where:
 				// - Because the block toolbar uses createPortal to populate the block toolbar fills, we can't rely on the React event bubbling to hit the onKeyDown listener for the block toolbar
 				// - Since we can't use the React tree, we use the DOM tree which _should_ handle the event bubbling correctly from a `createPortal` element.