parsing error when attr definition is missing

[srearl]

the following error is a real hassle to track down, seems that we could flag this in read_attributes or the create functions so that we catch it before we build the eml/xml

occurred when was present but was empty

[2] "Element 'attributeDefinition': [facet 'minLength'] The value has a length of '0'; this underruns the allowed minimum length of '1'."
[3] "Element 'attributeDefinition': [facet 'pattern'] The value '' is not accepted by the pattern '[\s][\S][\s\S]'."
[4] "Element 'definition': [facet 'minLength'] The value has a length of '0'; this underruns the allowed minimum length of '1'."
[5] "Element 'definition': [facet 'pattern'] The value '' is not accepted by the pattern '[\s][\S][\s\S]'."