Handle empty string ("") in observationData VIPSUTV-631

src/main/java/no/nibio/vips/logic/entity/Observation.java

@@ -444,7 +444,7 @@ public class Observation implements Serializable, no.nibio.vips.observation.Obse
     @Column(name = "observation_data")
     @Override
     public String getObservationData() {
-        return observationData;
+        return this.observationData != null && this.observationData.replaceAll("\"", "").trim().length() > 0 ? this.observationData : null;
     }
 
     /**