Bug 199021 Error message pops up several times when click an invalid dataset
Description: There is a sqlserver datasource and dataset, remove the jtds driver to let the dataset invalid. Double click on the dataset, the error message will pop up serveral times. Build version:2.2.0.v20070807-0630 Steps to reproduce: 1. Create a sqlserver datasource and dataset. 2. Remove the jtds driver, and the dataset will be invalid. 3. Double click on the dataset. Expect result: Error message pops up once to indicate the problem. Actual result: Error message pops up serveral times.
data/org.eclipse.birt.report.data.oda.jdbc.ui/src/org/eclipse/birt/report/data/oda/jdbc/ui/editors/SQLDataSetEditorPage.java
{
			selectNode( rootNode );
		}
	}
	/**
	 * 
	 * @return
	 */
	private DataSetDesign getDataSetDesign( )
	{
		if ( dataSetDesign == null )
			dataSetDesign = this.getInitializationDesign( );
		return dataSetDesign;
	}
	/**
	 * populate shema list if the schema is supported
	 * 
	 */
	protected void populateSchemaList( )
	{
		if ( rootNode != null )
		{
			removeTreeItem( rootNode );
		}
		if ( JdbcPlugin.getDefault( )
				.getPluginPreferences( )
				.getString( DateSetPreferencePage.SCHEMAS_PREFETCH_CONFIG )
				.equals( ENABLED ) )
		{
			getAvailableSchema( );