The error free fix is:
go to line 329 in admin/manufacturers.php
Find:
PHP Code:
      <?php if (empty($action) && !empty($mInfo)) { ?>
        <div class="col-sm-12 text-right">
          <a href="<?php echo zen_href_link(FILENAME_MANUFACTURERS, ($currentPage != 'page=' $currentPage '&' '') . 'mID=' $mInfo->manufacturers_id '&action=new'); ?>" class="btn btn-primary" role="button"><?php echo IMAGE_INSERT?></a>
        </div>
      <?php ?>
Replace the above with:

PHP Code:
      <?php if (empty($action) && !empty($mInfo)) { ?>
        <div class="col-sm-12 text-right">
    <a href="<?php echo zen_href_link(FILENAME_MANUFACTURERS, ($currentPage != 'page=' $currentPage '&' '') . 'mID=' $mInfo->manufacturers_id '&action=new'); ?>" class="btn btn-primary" role="button"><?php echo IMAGE_INSERT?></a>
        </div>
      <?php }else{ ?>
      <div class="col-sm-12 text-right">
      <a href="<?php echo zen_href_link(FILENAME_MANUFACTURERS, ($currentPage != 'page=' $currentPage '&' '') . 'mID=&action=new'); ?>" class="btn btn-primary" role="button"><?php echo IMAGE_INSERT?></a>
        </div>
      <?php ?>
Hope this helps.