Export select fields yields array_merge errors

when exporting contacts using the select fields option, you get a series of warnings re: the first argument of the array_merge

to fix, replace lines 586-591 with:

if ( isset($relationshipType->$direction) )

{ $relatedFields = array_merge((array)$relatedMapperFields[$relationshipType->$direction], (array)$relationshipCustomFields); }

else

{ $target_type = 'contact_type_'.$second; $relatedFields = array_merge((array)$relatedMapperFields[$relationshipType->$target_type], (array)$relationshipCustomFields); }