Bug 161191 Null is inserted when drag columns to query text with ctrl key pressed
Description: Null is inserted when drag columns to query text with ctrl key pressed Steps to reproduce: 1. New a data source. 2. New a dataset. 3. Press and hold ctrl key, select OFFICECODE and CITY columns, drag to query text. Expected result: "CLASSICMODELS.OFFICES.OFFICECODE,CLASSICMODELS.OFFICES.CITY" is inserted in query text. Actual result: "null,CLASSICMODELS.OFFICES.OFFICECODE,CLASSICMODELS.OFFICES.CITY" is inserted
data/org.eclipse.birt.report.data.oda.jdbc.ui/src/org/eclipse/birt/report/data/oda/jdbc/ui/editors/SQLDataSetEditorPage.java
*  
	 */
	public void addDropSupportToViewer( )
	{
		final StyledText text = viewer.getTextWidget( );
		DropTarget dropTarget = new DropTarget( text, DND.DROP_COPY | DND.DROP_DEFAULT );
		dropTarget.setTransfer( new Transfer[]{TextTransfer.getInstance( )} );
		dropTarget.addDropListener( new DropTargetAdapter( ) {
			public void dragEnter( DropTargetEvent event )
			{
				text.setFocus( );
				if ( event.detail == DND.DROP_DEFAULT )
					event.detail = DND.DROP_COPY;
				if ( event.detail != DND.DROP_COPY )
					event.detail = DND.DROP_NONE;
			}
			public void dragOver( DropTargetEvent event )
			{
				event.feedback = DND.FEEDBACK_SCROLL
						| DND.FEEDBACK_SELECT;
			}
			public void dragOperationChanged( DropTargetEvent event )
			{
				dragEnter( event );
			}
			public void drop( DropTargetEvent event )
			{
				if ( event.data instanceof String )
					insertText( (String) event.data );
			}