diff --git a/src/main/java/org/gcube/portlets/user/td/tablewidget/client/rows/DuplicatesRowsPanel.java b/src/main/java/org/gcube/portlets/user/td/tablewidget/client/rows/DuplicatesRowsPanel.java
index 8761451..4e659e8 100644
--- a/src/main/java/org/gcube/portlets/user/td/tablewidget/client/rows/DuplicatesRowsPanel.java
+++ b/src/main/java/org/gcube/portlets/user/td/tablewidget/client/rows/DuplicatesRowsPanel.java
@@ -139,7 +139,7 @@ public class DuplicatesRowsPanel extends FramedPanel {
 		deleteButton.addSelectHandler(deleteHandler);
 
 		// Validates Button
-		validatesButton = new TextButton("Validates");
+		validatesButton = new TextButton("Validate");
 		SelectHandler validatesHandler = new SelectHandler() {
 
 			public void onSelect(SelectEvent event) {
@@ -202,7 +202,13 @@ public class DuplicatesRowsPanel extends FramedPanel {
 	}
 
 	protected void onDeleteDuplicate() {
-		duplicatesSession = new DuplicatesSession(trId, getSelectedItems(),
+		ArrayList<ColumnData> col=getSelectedItems();
+		if(col==null||col.size()<1){
+			alert("Attention",
+					"Attention no column selected!");
+			return;
+		}
+		duplicatesSession = new DuplicatesSession(trId, col,
 				DuplicatesSession.DuplicateOp.DELETE);
 
 		TDGWTServiceAsync.INSTANCE.startDuplicates(duplicatesSession,
@@ -227,7 +233,13 @@ public class DuplicatesRowsPanel extends FramedPanel {
 	
 	
 	protected void onValidatesDuplicate() {
-		duplicatesSession = new DuplicatesSession(trId, getSelectedItems(),
+		ArrayList<ColumnData> col=getSelectedItems();
+		if(col==null||col.size()<1){
+			alert("Attention",
+					"Attention no column selected!");
+			return;
+		}
+		duplicatesSession = new DuplicatesSession(trId, col,
 				DuplicatesSession.DuplicateOp.VALIDATE);
 
 		TDGWTServiceAsync.INSTANCE.startDuplicates(duplicatesSession,