diff --git a/wp-admin/edit-form-blocks.php b/wp-admin/edit-form-blocks.php
index 8dc7da46f4..bc01ea11e4 100644
--- a/wp-admin/edit-form-blocks.php
+++ b/wp-admin/edit-form-blocks.php
@@ -197,11 +197,13 @@ if ( $editor_styles && current_theme_supports( 'editor-styles' ) ) {
 				);
 			}
 		} else {
-			$file     = get_theme_file_path( $style );
-			$styles[] = array(
-				'css'     => file_get_contents( get_theme_file_path( $style ) ),
-				'baseURL' => get_theme_file_uri( $style ),
-			);
+			$file = get_theme_file_path( $style );
+			if ( file_exists( $file ) ) {
+				$styles[] = array(
+					'css'     => file_get_contents( $file ),
+					'baseURL' => get_theme_file_uri( $style ),
+				);
+			}
 		}
 	}
 }
diff --git a/wp-includes/blocks.php b/wp-includes/blocks.php
index e584dc377d..fe1cb685ee 100644
--- a/wp-includes/blocks.php
+++ b/wp-includes/blocks.php
@@ -283,7 +283,7 @@ function _restore_wpautop_hook( $content ) {
  * @since 5.0.0
  *
  * @param string $content Content to test.
- * @return int The block format version.
+ * @return int The block format version is 1 if the content contains one or more blocks, 0 otherwise.
  */
 function block_version( $content ) {
 	return has_blocks( $content ) ? 1 : 0;
diff --git a/wp-includes/version.php b/wp-includes/version.php
index 4889597fcb..256ce872a9 100644
--- a/wp-includes/version.php
+++ b/wp-includes/version.php
@@ -13,7 +13,7 @@
  *
  * @global string $wp_version
  */
-$wp_version = '5.1-alpha-44269';
+$wp_version = '5.1-alpha-44270';
 
 /**
  * Holds the WordPress DB revision, increments when changes are made to the WordPress DB schema.