Ordenanzas en vigor

S'ha produït un error mentre es processava la plantilla. 
?sort failed at sequence index 0: Values used for sorting must be numbers, strings, date/times or booleans.

----
FTL stack trace ("~" means nesting-related):
	- Failed at: #list cur_ordenanza.getSiblings()?sor...  [in template "20116#20152#48838" at line 9, column 29]
----
1<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/font-awesome/4.4.0/css/font-awesome.min.css"> 
2 
3<#if tipoordenanza.getSiblings()?has_content> 
4	<#list tipoordenanza.getSiblings() as cur_tipoordenanza> 
5	    <h2>${cur_tipoordenanza.getData()}</h2> 
6    		<#list cur_tipoordenanza.getChildren() as cur_ordenanza> 
7		        <#if cur_ordenanza.getSiblings()?has_content> 
8		        <ul> 
9		            <#list cur_ordenanza.getSiblings()?sort as datos_ordenanza> 
10		            <li><a href="${datos_ordenanza.documento.getData()}">${datos_ordenanza.getData()}.pdf <i class="fas fa-file-pdf"></i></a> </li> 
11		            </#list>     
12		        </#if> 
13		         
14	        </#list> 
15	        </ul> 
16    </#list> 
17</#if>