Checking of the availability of a Chained converter not sub converters based will lead to the following NPE:
java.lang.NullPointerException at org.nuxeo.ecm.core.convert.service.ConversionServiceImpl.isConverterAvailable(ConversionServiceImpl.java:254) at org.nuxeo.ecm.core.convert.service.ConversionServiceImpl.isConverterAvailable(ConversionServiceImpl.java:224) at org.nuxeo.ecm.core.convert.service.ConversionServiceImpl.convert(ConversionServiceImpl.java:151)