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
/**
	 *  Create Metadata Provider
	 */
	protected void createMetaDataProvider( )
	{
		if ( metaDataProvider == null )
		{
			metaDataProvider = new JdbcMetaDataProvider(null);		
		}
	}
	
	/**
	 *  Initializes the Jdbc related information , used  by this page
	 * ( such as the Jdbc Connection , Catalog Name etc )
	 * @param curDataSourceHandle
	 *
	 */
	protected void resetJdbcInfo(DataSourceDesign curDataSourceDesign)
	{
		if( metaDataProvider != null )
		{
			metaDataProvider.closeConnection( );
			metaDataProvider = null;
			createMetaDataProvider( );
			jdbcConnection = connectMetadataProvider( metaDataProvider, curDataSourceDesign);
			
			
			tableList = null;
			schemaList = null;
			schemaCombo.removeAll();