In the server/<config>/conf/jboss-service.xml file there is mbean's attributes configured as following:

<server>
<mbean ... name="jboss:service=Naming" ...>
...
<attribute name="BindAddress">
<value-factory bean="ServiceBindingManager" method="getStringBinding">
<parameter>jboss:service=Naming</parameter>
<parameter>Port</parameter>
<parameter><null/></parameter>
</value-factory>
</attribute>
...
</mbean>
...
</server>

This exact configuration is fine. But while I change element formatting as follows, the </null> parameter parsing fails.
...
<attribute name="BindAddress">
<value-factory bean="ServiceBindingManager" method="getStringBinding">
<parameter>jboss:service=Naming</parameter>
<parameter>Port</parameter>
<parameter>
<null/>
</parameter>
</value-factory>
</attribute>
...

It seems the parser that parses this file doesn't ignore white-spaces around the <null/> element and the mbean behaves in different way.