preg_match(): Passing null – and – strlen(): Passing null

( ! ) Deprecated: preg_match(): Passing null to parameter #2 ($subject) of type string is deprecated in /website/wp-includes/class-wp-block-parser.php on line 261
Call Stack
#	Time	Memory	Function	Location
1	0.0002	405208	{main}( )	.../index.php:0
2	0.0004	406696	require( '/website/wp-blog-header.php )	.../index.php:17
3	0.3817	68439288	require_once( '/website/wp-includes/template-loader.php )	.../wp-blog-header.php:19
4	0.3824	68447184	include( '/website/wp-content/themes/wp-bootstrap-starter-child/front-page.php )	.../template-loader.php:106
5	0.3825	68449728	get_header( $name = ???, $args = ??? )	.../front-page.php:31
6	0.3825	68450104	locate_template( $template_names = [0 => 'header.php'], $load = TRUE, $load_once = TRUE, $args = [] )	.../general-template.php:48
7	0.3825	68450232	load_template( $_template_file = '/website/wp-content/themes/wp-bootstrap-starter-child/header.php', $load_once = TRUE, $args = [] )	.../template.php:720
8	0.3827	68484832	require_once( '/website/wp-content/themes/wp-bootstrap-starter-child/header.php )	.../template.php:785
9	0.3935	69080176	wp_head( )	.../header.php:122
10	0.3935	69080176	do_action( $hook_name = 'wp_head' )	.../general-template.php:3053
11	0.3935	69080552	WP_Hook->do_action( $args = [0 => ''] )	.../plugin.php:517
12	0.3935	69080552	WP_Hook->apply_filters( $value = '', $args = [0 => ''] )	.../class-wp-hook.php:334
13	0.3935	69082000	wp_enqueue_scripts( '' )	.../class-wp-hook.php:310
14	0.3935	69082000	do_action( $hook_name = 'wp_enqueue_scripts' )	.../script-loader.php:2225
15	0.3935	69082376	WP_Hook->do_action( $args = [0 => ''] )	.../plugin.php:517
16	0.3935	69082376	WP_Hook->apply_filters( $value = '', $args = [0 => ''] )	.../class-wp-hook.php:334
17	0.3969	69132944	UAGB_Front_Assets->enqueue_asset_files( '' )	.../class-wp-hook.php:310
18	0.3969	69132944	UAGB_Post_Assets->enqueue_scripts( )	.../class-uagb-front-assets.php:166
19	0.3969	69132944	parse_blocks( $content = NULL )	.../class-uagb-post-assets.php:389
20	0.3969	69133072	WP_Block_Parser->parse( $document = NULL )	.../blocks.php:1155
21	0.3969	69133072	WP_Block_Parser->proceed( )	.../class-wp-block-parser.php:78
22	0.3969	69133072	WP_Block_Parser->next_token( )	.../class-wp-block-parser.php:100
23	0.3969	69133104	preg_match( $pattern = '/<!--\\s+(?P<closer>\\/)?wp:(?P<namespace>[a-z][a-z0-9_-]*\\/)?(?P<name>[a-z][a-z0-9_-]*)\\s+(?P<attrs>{(?:(?:[^}]+|}+(?=})|(?!}\\s+\\/?-->).)*+)?}\\s+)?(?P<void>\\/)?-->/s', $subject = NULL, $matches = NULL, $flags = 256, $offset = 0 )	.../class-wp-block-parser.php:261

( ! ) Deprecated: strlen(): Passing null to parameter #1 ($string) of type string is deprecated in /website/wp-includes/class-wp-block-parser.php on line 333
Call Stack
#	Time	Memory	Function	Location
1	0.0002	405208	{main}( )	.../index.php:0
2	0.0004	406696	require( '/website/wp-blog-header.php )	.../index.php:17
3	0.3817	68439288	require_once( '/website/wp-includes/template-loader.php )	.../wp-blog-header.php:19
4	0.3824	68447184	include( '/website/wp-content/themes/wp-bootstrap-starter-child/front-page.php )	.../template-loader.php:106
5	0.3825	68449728	get_header( $name = ???, $args = ??? )	.../front-page.php:31
6	0.3825	68450104	locate_template( $template_names = [0 => 'header.php'], $load = TRUE, $load_once = TRUE, $args = [] )	.../general-template.php:48
7	0.3825	68450232	load_template( $_template_file = '/website/wp-content/themes/wp-bootstrap-starter-child/header.php', $load_once = TRUE, $args = [] )	.../template.php:720
8	0.3827	68484832	require_once( '/website/wp-content/themes/wp-bootstrap-starter-child/header.php )	.../template.php:785
9	0.3935	69080176	wp_head( )	.../header.php:122
10	0.3935	69080176	do_action( $hook_name = 'wp_head' )	.../general-template.php:3053
11	0.3935	69080552	WP_Hook->do_action( $args = [0 => ''] )	.../plugin.php:517
12	0.3935	69080552	WP_Hook->apply_filters( $value = '', $args = [0 => ''] )	.../class-wp-hook.php:334
13	0.3935	69082000	wp_enqueue_scripts( '' )	.../class-wp-hook.php:310
14	0.3935	69082000	do_action( $hook_name = 'wp_enqueue_scripts' )	.../script-loader.php:2225
15	0.3935	69082376	WP_Hook->do_action( $args = [0 => ''] )	.../plugin.php:517
16	0.3935	69082376	WP_Hook->apply_filters( $value = '', $args = [0 => ''] )	.../class-wp-hook.php:334
17	0.3969	69132944	UAGB_Front_Assets->enqueue_asset_files( '' )	.../class-wp-hook.php:310
18	0.3969	69132944	UAGB_Post_Assets->enqueue_scripts( )	.../class-uagb-front-assets.php:166
19	0.3969	69132944	parse_blocks( $content = NULL )	.../class-uagb-post-assets.php:389
20	0.3969	69133072	WP_Block_Parser->parse( $document = NULL )	.../blocks.php:1155
21	0.3969	69133072	WP_Block_Parser->proceed( )	.../class-wp-block-parser.php:78
22	0.3970	69133328	WP_Block_Parser->add_freeform( $length = ??? )	.../class-wp-block-parser.php:111