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 ( ( cachedSearchTxt == searchTxt.getText( ) || ( cachedSearchTxt != null && cachedSearchTxt.equals( searchTxt.getText( ) ) ) )
					&& ( cachedDbType == getSelectedDbType( ) || ( cachedDbType != null && cachedDbType.equals( getSelectedDbType( ) ) ) ) )
			{
				if ( schemaList != null && schemaList.size( ) > 0 )
				{
					if ( cachedSchemaComboIndex == schemaCombo.getSelectionIndex( ) )
					{
						return;
					}
				}
				else
					return;
			}
		}
		 
		
		RemoveAllAvailableDbObjects( );
		setRootElement( );
		setRefreshInfo( );
		if ( isSchemaSupported )
		{
			populateSchemaList( );
		}
		else
		{
			populateTableList( );
		}
		addFetchDbObjectListener( );
		
		if ( rootNode != null )