code in sidebar interrupting the main loop

i’ve inserted some code into my sidebar to bring up a list of all posts, sorted by year. the problem is that it interrupts my main loop – when clicking on both single posts as well as category links, it simply shows all posts. i understand why this is – i’ve started a loop in the sidebar which interferes with the main loop. here is the code i’ve inserted into the sidebar:

<?php query_posts(array('nopaging' => 1, /* we want all posts, so disable paging. Order by date is default */));
$prev_year = null;
if ( have_posts() ) {
   while ( have_posts() ) {
      the_post();
      $this_year = get_the_date('Y');
      if ($prev_year != $this_year) {
          // Year boundary
          if (!is_null($prev_year)) {
             // A list is already open, close it first
             echo '</ul>';
          }
          echo '<b>' . $this_year . '</b>';
          echo '<ul>';
      }
      echo '<li><a href="'. get_permalink() .'">' . get_the_title() .'</a></li>';
      $prev_year = $this_year;
   }
   echo '</ul>';
} ?>

The problem is, I don’t know how to end this loop without getting a syntax error?

Here is a link to a single post, which you can see does not return just the post but every post (so far there are only two posts):

https://www.pprbmb.com/wordpress/exhibition-title/