Use Item.ANY instead of null

tested with the production db dump on the items mentions in the issue
(11234/1-5537). It was returning:
```
The script has started
Item '11234/1-5537' has no handle assigned.
```

because it's dc.identifier.uri.*

Author: kosarko

dspace-api/src/main/java/org/dspace/administer/ItemVersionLinker.java

@@ -355,7 +355,7 @@ private boolean isUUID(String itemID) {
     }
 
     private String getHandleRef(Item item) {
-        return itemService.getMetadata(item, "dc", "identifier", "uri", null)
+        return itemService.getMetadata(item, "dc", "identifier", "uri", Item.ANY)
                 .stream()
                 .findFirst()
                 .map(MetadataValue::getValue)