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
}
		} );
		filterComboViewer.setLabelProvider( new LabelProvider( ) {
			public String getText( Object inputElement )
			{
				DbType dbType = (DbType) inputElement;
				return dbType.getName( );
			}
		} );
		filterComboViewer.setInput( dbTypeList );
		
		filterComboViewer.getCombo( ).select( 0 );
	}
	/**
	 * This method is invoked when the find button is clicked It populates the
	 * Available Data Base obecets ( in the Tree control )
	 */
	protected void populateAvailableDbObjects()
	{
		DataSetDesign dataSetDesign = getDataSetDesign( );
		DataSourceDesign curDataSourceDesign = dataSetDesign.getDataSourceDesign( );
		
		if ( curDataSourceDesign == prevDataSourceDesign )
		{
			if ( ( cachedSearchTxt == searchTxt.getText( ) || ( cachedSearchTxt != null && cachedSearchTxt.equals( searchTxt.getText( ) ) ) )
					&& ( cachedDbType == getSelectedDbType( ) || ( cachedDbType != null && cachedDbType.equals( getSelectedDbType( ) ) ) ) )
			{
				if ( schemaList != null && schemaList.size( ) > 0 )
				{
					if ( cachedSchemaComboIndex == schemaCombo.getSelectionIndex( ) )