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
*/
	private void RemoveAllAvailableDbObjects( )
	{
		if ( availableDbObjectsTree != null )
			availableDbObjectsTree.removeAll( );
	}
	/**
	 * Gets the list of schema objects
	 */
	private void getAvailableSchema( )
	{
		if ( isSchemaSupported )
		{
			ResultSet schemas = metaDataProvider.getAllSchema( );
			schemaList = getAllSchemaList( schemas );
		}
	}
	/**
	 * 
	 * @param schemaName
	 * @param schemaTreeItem
	 */
	protected void populateTableList( String schemaName, TreeItem schemaTreeItem )
	{
		if ( schemaTreeItem != null )
		{
			removeTreeItem( schemaTreeItem );
		}
		String namePattern = null;
		String[] tableType = null;