Struts2: tag.getValidators("${tagName}") error

During the execution (and if you have the debug mode activate) you are getting an error similar to:


----------
==> list tag.getValidators("${tagName}") as validator [on line 46, column 9 in template/xhtml/form-close-validate.ftl]
in include "/${parameters.templateDir}/xhtml/form-close-validate.ftl" [on line 25, column 1 in template/xhtml/form-close.ftl]
----------
...several lines...
Caused by: java.lang.NullPointerException......

I've tried to found the real cause unsucessfully but finally I've follow the next steps to solve the issue:

The -validation.xml file is with the .java class
s
The message in the -validation.xml file is properly set	${getText("800_u01ra_error_001")}
My solution has been: remove validate="true" from the form	s:form action="Peticio01pas1"  method="post" name="selectfile">

For complete information about struts2 validation you could visit the following link:
http://struts.apache.org/2.3.4.1/docs/validation.html