[BitBucket user: Alain Mazy]
[BitBucket date: 2018-04-23.08:24:55]

The fact that the find fails in case one of the searched dicom tag is null is also affecting the search in OrthancExplorer2:

- upload an instance from the ORTHO patient (attached),
- perform the following `tools/find` request: 
```
curl 'http://localhost:8042/tools/find' --data-binary '{"Level":"Patient","CaseSensitive":false,"Query":{"AccessionNumber":"*","PatientBirthDate":"*","PatientID":"*","PatientName":"*O*","PatientSex":"*","StudyDate":"*","StudyDescription":"*"},"Limit":10,"Since":0}'
```
- this will return no result
- note that this happens with all anonymized instances since they usually lose their `PatientSex` and `PatientBirthDate`