Generated side menu creates invalid html ul list

[JakubJecminek]

https://github.com/alkacon/modules-v8/blob/branch_8_5_x/modules/com.alkacon.opencms.v8.template3/resources/system/modules/com.alkacon.opencms.v8.template3/elements/menu/nav_side.jsp

from demo template 3 example of the problem:

   <li><a href="/flower-en/flower-search/solr-integration/" >Flower Search</a>    
    </li>   
   <li><a href="/flower-en/flower-subscription/" >Flower Subscription</a>  
  </li></ul></li></ul>
  </li>
 </ul>

As you can see on the end of the ul list thare are redundant html tags. This issue is still valid for 8.5.1.

[JakubJecminek]

I did some experiments with nav_side.jsp both on demo flower site and our other projects and I think I've found a solution for this problem. After my change in nav_side.jsp the previous html snippet looks like this

<li><a href="/opencms/opencms/flower-en/flower-search/solr-integration/" >Flower Search</a>             
                </li>           
<li><a href="/opencms/opencms/flower-en/flower-subscription/" >Flower Subscription</a>      
</li></ul>  

which is valid html ul list. I test it with several different pages many items in navigation and it still produce valid html list. Here is changed nav_side.jsp:

<%@page buffer="none" session="false" taglibs="c,cms,fn" %>
<c:set var="navStartLevel" ><cms:property name="NavStartLevel" file="search" default="0" /></c:set>
<cms:navigation type="treeForFolder" startLevel="${navStartLevel + 1}" endLevel="${navStartLevel + 3}" var="nav"/>
<div id="nav_left">
    <ul>            
        <c:set var="oldLevel" value="" />
        <c:forEach items="${nav.items}" var="elem">
            <c:set var="currentLevel" value="${elem.navTreeLevel}" />
            <c:choose>
                <c:when test="${empty oldLevel}"></c:when>
                <c:when test="${currentLevel > oldLevel}"><ul></c:when>
                <c:when test="${currentLevel == oldLevel}"></li></c:when>
                <c:when test="${oldLevel > currentLevel}">
                    <c:forEach begin="${currentLevel + 1}" end="${oldLevel}"></li></ul></c:forEach></li>
                </c:when>
            </c:choose>

            <li><a href="<cms:link>${elem.resourceName}</cms:link>" <c:if test="${!elem.navigationLevel && nav.isActive[elem.resourceName]}">class="current"</c:if>>${elem.navText}</a>

            <c:set var="oldLevel" value="${currentLevel}" />
        </c:forEach>

        <c:forEach begin="${navStartLevel+1}" end="${oldLevel}"></li></ul></c:forEach>  
</div>

I could create pull request if you find this change valid.