Index: wp-includes/class-wp-query.php
===================================================================
--- wp-includes/class-wp-query.php	(revision 41155)
+++ wp-includes/class-wp-query.php	(working copy)
@@ -3206,7 +3206,7 @@
 	 */
 	public function rewind_posts() {
 		$this->current_post = -1;
-		if ( $this->post_count > 0 ) {
+		if ( !empty( $this->posts[0] )  && isset( $this->posts[0] ) && $this->post_count > 0  ) {
 			$this->post = $this->posts[0];
 		}
 	}