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
dragSource.addDragListener( new DragSourceAdapter( ) {
			public void dragStart( DragSourceEvent event )
			{
				TreeItem[] selection = availableDbObjectsTree.getSelection( );
				
				selectionMac = availableDbObjectsTree.getSelection( );
				
				if ( selection.length > 0 )
				{
					if ( selection[0].getData( ) instanceof DbObject )
					{
						if ( !isAcceptableDbObjectType( getDbObjectType( selection[0].getData( ) ) ) )
						{
							event.doit = false;
							return;
						}
						else
						{
							if ( !isDbObjectTreeValid( selection,
									getDbObjectType( selection[0].getData( ) ) ) )
							{
								event.doit = false;
								return;
							}
						}
					}
					else if ( selection[0].getData( ) instanceof Procedure )
					{
						for ( int i = 1; i < selection.length; i++ )
						{