Error messages when adding code to function.php or trying to delete inactive plugin files

Question

Error message below:

Warning: Cannot modify header information - headers already sent by (output started at /home/content/79/7603579/html/listings/wp-content/themes/OIB theme/functions.php:519) in /home/content/79/7603579/html/listings/wp-includes/pluggable.php on line 897

EDIT: Code around functions.php line 519:

    <small><?php echo $value['desc']; ?></small>
    <div class="clearfix"></div>
    </div> 
    <?php break; 
case "section":
    $i++; ?>
    <div class="rm_section">
       <div class="rm_title">
         <h3><img src="<?php bloginfo('template_directory')?>/functions/images/trans.gif" class="inactive" alt="""><?php echo $value['name']; ?></h3>
         <span class="submit">
            <input name="save<?php echo $i; ?>" type="submit" value="Save changes" />
         </span>
         <div class="clearfix"></div>
      </div>
      <div class="rm_options">
    <?php break;
   } 
} ?>

And the fix, per comment below, removed this code:

function cpt_Search_category_Filter($query) {
   $post_type = array('post','business_sold');
   if ($query->is_search || $query->is_category) {
      $query->set('post_type', $post_type);
   };
      return $query;
};
add_filter('pre_get_posts','cpt_Search_category_Filter');

Answer 1

Your functions.php file is outputting instead of returning something, on line 519.

Can you post whatever code/functions are around Line 519?

EDIT:

You have a syntax error in your cpt_Search_category_Filter() function. You have a couple stray semi-colons after closing braces.

Change this:

function cpt_Search_category_Filter($query) {
   $post_type = array('post','business_sold');
   if ($query->is_search || $query->is_category) {
      $query->set('post_type', $post_type);
   };
      return $query;
};
add_filter('pre_get_posts','cpt_Search_category_Filter');

to this:

function cpt_Search_category_Filter($query) {
   $post_type = array('post','business_sold');
   if ($query->is_search || $query->is_category) {
      $query->set('post_type', $post_type);
   }
      return $query;
}
add_filter('pre_get_posts','cpt_Search_category_Filter');