diff --git a/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/CreateDatasetForm.java b/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/CreateDatasetForm.java
index 284a788..ec17a83 100644
--- a/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/CreateDatasetForm.java
+++ b/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/CreateDatasetForm.java
@@ -72,7 +72,7 @@ import com.google.gwt.user.client.ui.Widget;
  * @author Costantino Perciante at ISTI-CNR (costantino.perciante@isti.cnr.it)
  */
 public class CreateDatasetForm extends Composite{
-
+	
 	/**
 	 * Create a remote service proxy to talk to the server-side ckan service.
 	 */
@@ -152,6 +152,8 @@ public class CreateDatasetForm extends Composite{
 	@UiField Icon infoIconResources;
 	@UiField FocusPanel focusPanelResources;
 	@UiField Popover popoverResources;
+	
+	protected static final String ERROR_PRODUCT_CREATION = "There was an error while trying to publish your product, sorry.. Retry later";
 
 	// tab panel 
 	private TabPanel tabPanel; 
@@ -756,17 +758,14 @@ public class CreateDatasetForm extends Composite{
 						}
 
 					}else{
-
-						alertOnCreate("Unable to create this product, maybe it already exists?", AlertType.ERROR);
+						alertOnCreate(ERROR_PRODUCT_CREATION, AlertType.ERROR);
 					}
 
 				}
 
 				@Override
 				public void onFailure(Throwable caught) {
-
-					alertOnCreate("Unable to create this product, maybe it already exists?", AlertType.ERROR);
-
+					alertOnCreate(ERROR_PRODUCT_CREATION, AlertType.ERROR);
 				}
 			});
 		}
diff --git a/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/MetaDataFieldSkeleton.java b/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/MetaDataFieldSkeleton.java
index 7994bf0..10b9b6b 100644
--- a/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/MetaDataFieldSkeleton.java
+++ b/src/main/java/org/gcube/portlets/widgets/ckandatapublisherwidget/client/ui/MetaDataFieldSkeleton.java
@@ -237,10 +237,10 @@ public class MetaDataFieldSkeleton extends Composite{
 		if(holder.getClass().equals(ListBox.class)){
 			value = ((ListBox)holder).getSelectedItemText();
 
-			// if it was not mandatory but there was no choice, returning null
+			// if it was not mandatory but there was no choice, returning empty string
 			if(!field.getMandatory())
 				if(value.equals("Select " + field.getFieldName()))
-					return null;
+					return "";
 
 		}
 		else if(holder.getClass().equals(TextBox.class))