Improve error message when DN generator cannot generate DN because of an empty field

Adapter import all entities for adapter failed.
Adapter import all entities for adapter a5ce2427-2d82-417b-8371-7c0e6d7eb300 failed with reason Specified argument was out of the range of valid values.
Parameter name: attributeValue. Duration: 00:00:24.5312500
Error details:
System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: attributeValue
at Unify.Framework.IO.DistinguishedNameComponent..ctor(DNAttributeType attributeType, String attributeValue)
at Unify.Product.IdentityBroker.EntityFieldValueDistinguishedNameComponentGenerator`2.Transform(TEntity sourceValue)
at Unify.Product.IdentityBroker.EntityDistinguishedNameGenerator`2.<>c_DisplayClass7.<Transform>b_6(IEntityDistinguishedNameComponentGenerator`2 factory)
at System.Linq.Enumerable.<>c_DisplayClass12`3.<CombineSelectors>b_11(TSource x)
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.<SelectManyIterator>d__14`2.MoveNext()
at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
at System.Linq.Enumerable.ToArrayTSource(IEnumerable`1 source)
at Unify.Product.IdentityBroker.EntityDistinguishedNameGenerator`2.GetDistinguishedName(Func`2 componentRetrieval)
at Unify.Product.IdentityBroker.EntityDistinguishedNameGenerator`2.Transform(TEntity sourceValue)
at Unify.Product.IdentityBroker.DistinguishedNameAttributeMapper.MapAttributeValues(IEntity leftSideEntity, IEntity rightSideEntity)
at Unify.Product.IdentityBroker.ComposedDNAttributeMapper.MapAttributeValues(IEntity leftSideEntity, IEntity rightSideEntity)
at Unify.Product.IdentityBroker.EntityDistinguishedNameStaticRelationValueAdapterBase.TransformEntity(IEntity baseValue, ILookup`2 lookupResults)
at Unify.Product.IdentityBroker.EntityDistinguishedNameStaticRelationValueAdapterBase.<>c_DisplayClass7.<Transform>b_3(IEntity item)
at System.Linq.Enumerable.WhereSelectArrayIterator`2.MoveNext()
at System.Linq.Buffer`1..ctor(IEnumerable`1 source)
at System.Linq.Enumerable.ToArrayTSource(IEnumerable`1 source)
at Unify.Product.IdentityBroker.EntityDistinguishedNameStaticRelationValueAdapterBase.Transform(IEnumerable`1 sourceValue)
at Unify.Framework.AggregateValueAdapter`1.<Transform>b__0(T current, IValueAdapter`2 valueAdapter)
at System.Linq.Enumerable.AggregateTSource,TAccumulate(IEnumerable`1 source, TAccumulate seed, Func`3 func)
at Unify.Framework.AggregateValueAdapter`1.Transform(T baseValue)
at System.Linq.Enumerable.<>c_DisplayClass12`3.<CombineSelectors>b_11(TSource x)
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at Unify.Framework.Collections.EnumerableExtensions.<ActionOnLast>d__17`1.MoveNext()
at System.Linq.Enumerable.<SelectManyIterator>d__14`2.MoveNext()
at Unify.Framework.Collections.EnumerableExtensions.<ActionOnLast>d__17`1.MoveNext()
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at Unify.Framework.Collections.ActionOnExceptionEnumerator`1.MoveNext()
at Unify.Framework.Collections.EnumerableExtensions.<ActionOnLast>d__17`1.MoveNext()
at System.Linq.Enumerable.<SelectManyIterator>d__14`2.MoveNext()
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at Unify.Framework.Collections.ActionOnExceptionEnumerator`1.MoveNext()
at Unify.Framework.Collections.EnumerableExtensions.<ActionOnLast>d__17`1.MoveNext()
at System.Linq.Enumerable.WhereSelectEnumerableIterator`2.MoveNext()
at System.Linq.Enumerable.<SelectManyIterator>d__14`2.MoveNext()
at System.Linq.Enumerable.<ConcatIterator>d__71`1.MoveNext()
at Unify.Framework.IO.LDIFComponentFileGenerator`1.GenerateFile(TextWriter writer, IEnumerable`1 entries)
at Unify.Product.IdentityBroker.LDIFAdapterBase.<>c_DisplayClass14`1.<CreateLDIFComponentStream>b_13(Stream stream)
at Unify.Framework.IO.LazyEvaluationStream.Evaluate(Object obj)