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
if ( curDataSourceDesign != prevDataSourceDesign  )
		{
			RemoveAllAvailableDbObjects( );
			resetJdbcInfo( curDataSourceDesign );
			enableSchemaComponent( isSchemaSupported );
			setRootElement( );
			sourceViewerConfiguration.getContentAssistProcessor( )
					.setDataSourceHandle( curDataSourceDesign );
 
			populateAvailableDbObjects( );
			prevDataSourceDesign = curDataSourceDesign;
			try 
			{
				if ( metaDataProvider.getConnection( ) == null
						|| this.getDataSetDesign( ).getQueryText( ) == null
						|| this.getDataSetDesign( )
								.getQueryText( )
								.trim( )
								.length( ) == 0 )
					return;
				
				ResultSetMetaData meta = null;
				try
				{
					meta = this.metaDataProvider.getConnection( )
							.prepareStatement( this.getDataSetDesign( )
									.getQueryText( ) )
							.getMetaData( );
				}
				catch ( SQLException e )