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 initializeSchemaPrefetchConfig( )
	{
		if ( !JdbcPlugin.getDefault( )
				.getPluginPreferences( )
				.contains( DateSetPreferencePage.SCHEMAS_PREFETCH_CONFIG ) )
		{
			JdbcPlugin.getDefault( )
					.getPluginPreferences( )
					.setValue( DateSetPreferencePage.SCHEMAS_PREFETCH_CONFIG,
							ENABLED );
		}
	}
	/**
	 * Creates the composite, for displaying the list of available db objects
	 * 
	 * @param parent
	 */
	private void createTableSelectionComposite( Composite parent )
	{
		Composite tablescomposite = new Composite( parent, SWT.NONE );
		GridLayout layout = new GridLayout( );
		tablescomposite.setLayout( layout );
		{
			GridData data = new GridData( GridData.FILL_BOTH );
			data.grabExcessVerticalSpace = true;
			tablescomposite.setLayoutData( data );
		}
		
		Label dataSourceLabel = new Label( tablescomposite, SWT.LEFT );
		dataSourceLabel.setText( JdbcPlugin.getResourceString( "tablepage.label.availableItems" ) );