prevent warnings if value doesnt exist

src/Blocks/Block.php

@@ -209,7 +209,7 @@ public function __construct( $data, $post_id, $registry, $order, $parent ) {
 
 		$this->name            = $data['blockName'];
 		$this->postId          = $post_id;
-		$this->blockType       = $registry[ $this->name ];
+		$this->blockType       = $registry[ $this->name ] ?? null;
 		$this->originalContent = self::strip_newlines( $data['innerHTML'] );
 		$this->saveContent     = self::parse_inner_content( $data );
 		$this->order           = $order;