Added item name to error message (#2594)

Signed-off-by: Christoph Weitkamp <github@christophweitkamp.de>

bundles/org.openhab.core.ui/src/main/java/org/openhab/core/ui/internal/items/ItemUIRegistryImpl.java

@@ -372,7 +372,7 @@ public class ItemUIRegistryImpl implements ItemUIRegistry {
                 }
             }
         } catch (ItemNotFoundException e) {
-            logger.error("Cannot retrieve item for widget {}", w.eClass().getInstanceTypeName());
+            logger.error("Cannot retrieve item '{}' for widget {}", itemName, w.eClass().getInstanceTypeName());
         }
 
         boolean considerTransform = false;