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
}
			/**
			 * 
			 * @param dbObj
			 * @return
			 */
			private int getDbObjectType( Object dbObj )
			{
				return ( (DbObject) dbObj ).getType( );
			}
			/**
			 * 
			 * @param selection
			 * @param type
			 * @return
			 */
			private boolean isDbObjectTreeValid( TreeItem[] selection, int type )
			{
				for ( int i = 1; i < selection.length; i++ )
				{
					if ( !( selection[i].getData( ) instanceof DbObject ) )
					{
						return false;
					}
					DbObject temp = (DbObject) selection[i].getData( );
					if ( !isAcceptableDbObjectType( temp.getType( ) ) )
					{
						return false;
					}
					if ( temp.getType( ) != type && isTableOrView( type ) )