@Override
        public Object convert(Object existingDestinationFieldValue, Object sourceFieldValue, Class<?> destinationClass, Class<?> sourceClass) {
            MapperAwareSimpleInternal a = (MapperAwareSimpleInternal)sourceFieldValue;

            MapperAwareSimpleInternal b = new MapperAwareSimpleInternal();
            mapper.map(a, b);
            MapperAwareSimpleInternal b2 = new MapperAwareSimpleInternal();
            mapper.map(a, b2); //throws NPE in issue45
            return b2;
        }
Fixes issue 45

@see <a href="https://github.com/DozerMapper/dozer/issues/45">issue</a>
core/src/test/java/com/github/dozermapper/core/functional_tests/mapperaware/SecondUsingMapInternalTest.java