Ticket #43201: 43201.diff

src/wp-includes/media.php

@@ -1205 +1205 @@
         $sources = apply_filters( 'wp_calculate_image_srcset', $sources, $size_array, $image_src, $image_meta, $attachment_id );
 
         // Only return a 'srcset' value if there is more than one source.
-        if ( ! $src_matched || count( $sources ) < 2 ) {
+        if ( ! $src_matched || ! is_array( $sources ) || count( $sources ) < 2 ) {
                 return false;
         }