Blocks: Update default value for some fields in WP_Block_Type

Related to the issue with default values for the blocks registered on the server. By using null for some fields we can treat them as undefined on the client.

See: WordPress/gutenberg#22849.
Props aduth.
Fixes #48529. 


Built from https://develop.svn.wordpress.org/trunk@47907


git-svn-id: http://core.svn.wordpress.org/trunk@47681 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-includes/class-wp-block-type.php

@@ -32,9 +32,9 @@ class WP_Block_Type {
 
 	/**
 	 * @since 5.5.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $category = '';
+	public $category = null;
 
 	/**
 	 * @since 5.5.0
@@ -44,9 +44,9 @@ class WP_Block_Type {
 
 	/**
 	 * @since 5.5.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $icon = '';
+	public $icon = null;
 
 	/**
 	 * @since 5.5.0
@@ -104,25 +104,25 @@ class WP_Block_Type {
 	 * Block type editor script handle.
 	 *
 	 * @since 5.0.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $editor_script = '';
+	public $editor_script = null;
 
 	/**
 	 * Block type front end script handle.
 	 *
 	 * @since 5.0.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $script = '';
+	public $script = null;
 
 	/**
 	 * Block type editor style handle.
 	 *
 	 * @since 5.0.0
-	 * @var string
+	 * @var string|null
 	 */
-	public $editor_style = '';
+	public $editor_style = null;
 
 	/**
 	 * Block type front end style handle.
@@ -130,7 +130,7 @@ class WP_Block_Type {
 	 * @since 5.0.0
 	 * @var string
 	 */
-	public $style = '';
+	public $style = null;
 
 	/**
 	 * Constructor.

wp-includes/version.php

@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.5-alpha-47906';
+$wp_version = '5.5-alpha-47907';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.