Check if block theme

Author: mukeshpanchal27

plugins/auto-sizes/includes/improve-calculate-sizes.php

@@ -140,6 +140,11 @@ function auto_sizes_filter_image_tag( $content, array $parsed_block, WP_Block $b
  * @return string|false An improved sizes attribute or false if a better size cannot be calculated.
  */
 function auto_sizes_calculate_better_sizes( int $id, $size, string $align, int $resize_width, string $max_alignment ) {
+	// Bail early if not a block theme.
+	if ( ! wp_is_block_theme() ) {
+		return false;
+	}
+
 	// Without an image ID or a resize width, we cannot calculate a better size.
 	if ( 0 === $id && 0 === $resize_width ) {
 		return false;