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
/**
	 * initial dataset control
	 * 
	 */
	private void initializeControl( )
	{
		DEFAULT_MESSAGE = JdbcPlugin.getResourceString( "dataset.new.query" );
		setMessage( DEFAULT_MESSAGE, IMessageProvider.NONE );
		refreshPage( );
		prepareUI( );
	}
	
	/**
	 * Creates the composite, for displaying the list of available db objects
	 * 
	 * @param parent
	 */
	private void createTableSelectionComposite( Composite parent )
	{
		Composite tablescomposite = new Composite( parent, SWT.NONE );
		GridLayout layout = new GridLayout( );
		tablescomposite.setLayout( layout );
		{
			GridData data = new GridData( GridData.FILL_BOTH );
			data.grabExcessVerticalSpace = true;
			tablescomposite.setLayoutData( data );
		}
		
		Label dataSourceLabel = new Label( tablescomposite, SWT.LEFT );
		dataSourceLabel.setText( JdbcPlugin.getResourceString( "tablepage.label.availableItems" ) );