Added NULL as default value for 'location_type' (virtual node).

Signed-off-by: Cristiano Urban <cristiano.urban@inaf.it>

00-init.sql

@@ -112,7 +112,7 @@ CREATE TABLE deleted_node (
 
 CREATE TABLE location (
     location_id       SMALLSERIAL   NOT NULL,
-    location_type     LocationType  NOT NULL,
+    location_type     LocationType  default NULL,
     base_path         VARCHAR       NOT NULL,
     hostname          VARCHAR       NOT NULL,
     PRIMARY KEY (location_id)