Site Health: Use an integer value as a fallback in the available disk space check.

This avoids a few type problems further in the code: boolean divided by a number, or passing `false` to `size_format()` which is documented to accept integers or strings only.

Follow-up to [51815].

Props TobiasBg.
See #51857.
Built from https://develop.svn.wordpress.org/trunk@51898


git-svn-id: http://core.svn.wordpress.org/trunk@51491 1a063a9b-81f0-0310-95a4-ce76da25c4cd

wp-admin/includes/class-wp-site-health.php

@@ -1890,7 +1890,7 @@ class WP_Site_Health {
 	 * @return array The test results.
 	 */
 	public function get_test_available_updates_disk_space() {
-		$available_space       = function_exists( 'disk_free_space' ) ? (int) @disk_free_space( WP_CONTENT_DIR . '/upgrade/' ) : false;
+		$available_space       = function_exists( 'disk_free_space' ) ? (int) @disk_free_space( WP_CONTENT_DIR . '/upgrade/' ) : 0;
 		$available_space_in_mb = $available_space / MB_IN_BYTES;
 
 		$result = array(

wp-includes/version.php

@@ -16,7 +16,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.9-alpha-51897';
+$wp_version = '5.9-alpha-51898';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.