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
ArrayList dbTypeList = new ArrayList( );
		DbType tableType = new DbType( DbType.TABLE_TYPE,
				JdbcPlugin.getResourceString( "tablepage.text.tabletype" ) );
		DbType viewType = new DbType( DbType.VIEW_TYPE,
				JdbcPlugin.getResourceString( "tablepage.text.viewtype" ) );
		DbType allType = new DbType( DbType.ALL_TYPE,
				JdbcPlugin.getResourceString( "tablepage.text.All" ) );
		DbType procedureType = new DbType( DbType.PROCEDURE_TYPE,
				JdbcPlugin.getResourceString( "tablepage.text.procedure" ) );
		
		dbTypeList.add( allType );
		dbTypeList.add( tableType );
		dbTypeList.add( viewType );
		if ( metaDataProvider.isProcedureSupported( ) )
			dbTypeList.add( procedureType );
		filterComboViewer.setContentProvider( new IStructuredContentProvider( ) {
			public Object[] getElements( Object inputElement )
			{
				if ( inputElement != null )
				{
					return ( (ArrayList) inputElement ).toArray( );
				}
				return new DbType[]{};
			}
			public void dispose( )
			{
			}
			public void inputChanged( Viewer viewer, Object oldInput,
					Object newInput )
			{