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
}
	
	/**
	 * 
	 * @param b
	 */
	private void enableSchemaComponent( boolean b )
	{
		if ( b )
		{
			this.schemaCombo.setEnabled( true );
			this.schemaLabel.setEnabled( true );
		}
		else
		{
			this.schemaCombo.removeAll( );
			this.schemaCombo.setEnabled( false );
			this.schemaLabel.setEnabled( false );
		}
	}
	/**
	 * 
	 * @param filterComboViewer
	 */
	private void setFilterComboContents( ComboViewer filterComboViewer )
	{
		if ( filterComboViewer == null )
		{
			return;
		}