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
} );
		attachMenus( viewer );
        
        GridData data = new GridData(GridData.FILL_BOTH);
        viewer.getControl().setLayoutData(data);
        
        
        addDropSupportToViewer();
        
        viewer.getTextWidget( ).addKeyListener( new KeyListener( ) {
			public void keyPressed( KeyEvent e )
			{
				if ( isUndoKeyPress( e ) )
				{
					viewer.doOperation( ITextOperationTarget.UNDO );
				}
				else if ( isRedoKeyPress( e ) )
				{
					viewer.doOperation( ITextOperationTarget.REDO );
				}
			}
			private boolean isUndoKeyPress( KeyEvent e )
			{
				
				return ( ( e.stateMask & SWT.CONTROL ) > 0 )
						&& ( ( e.keyCode == 'z' ) || ( e.keyCode == 'Z' ) );
			}
			private boolean isRedoKeyPress( KeyEvent e )
			{