PL-5434 Do not show unsaved changes dialog If we click on cancel in CategoryAttributeEditor for new CategoryAttribute without any changes

Avoid default data type... 
#PL-5434

modules/global/src/com/haulmont/cuba/core/entity/CategoryAttribute.java

@@ -45,7 +45,7 @@ public class CategoryAttribute extends StandardEntity {
     private String enumeration;
 
     @Column(name = "DATA_TYPE")
-    private String dataType = PropertyType.STRING.name();
+    private String dataType;
 
     @Column(name = "IS_ENTITY")
     private Boolean isEntity;