Issue using BPM Generic Function for sort a list

Hello there

I am tryng to use default sort function an array list but I am getting an error.

My goal is sorting the input and delivering a sorted list as output.

Example:

Input:        

<Missao>

     <Localidades>

          <Sequencia>ZZ</Sequencia >

     </Localidades>

     <Localidades>

          <Sequencia >AA</Sequencia >

     </Localidades>

</Missao>

Output:

<Missao>

     <Localidades>

          <Sequencia>AA</Sequencia >

     </Localidades>

     <Localidades>

          <Sequencia>ZZ</Sequencia >

     </Localidades>

</Missao>

I am using following mapping script between Input and Output in my BPM process:

sort(Missao/Localidades,"Sequencia",false)

The sintax above is the same provided in SAP documentation for Generic Funcions:

Generic Functions - SAP NetWeaver Composition Environment Library - SAP Library

But I am getting following error:

Mapping failed
java.lang.NullPointerException: while trying to invoke the method java.lang.String.compareTo(java.lang.String) of a null object returned from com.sap.mapping.lib.execution.implementation.function.builtin.generic.NodeContentReader.read(com.sap.mapping.lib.execution.api.data.SourceNode)
com.sap.mapping.lib.execution.api.exception.TExecutionException
at GenericSort( StandardInvocation:invoker )
at ( DeepExpression )
at http://services.europ-assistance.com.br/fsm:Localidades( TerminalPart:expression )
at europ-assistance.com/dc_criar/Efetuar_Reserva/Processo_Efetuar_Reserva:Missao( BroadPart:child )
at ( BroadMapping )

I don’t understand why the null exception above occurs, the node Sequenciaisfilled and its cardinality is ok as well.

. .

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