Bug 161191 Null is inserted when drag columns to query text with ctrl key pressed
Description: Null is inserted when drag columns to query text with ctrl key pressed Steps to reproduce: 1. New a data source. 2. New a dataset. 3. Press and hold ctrl key, select OFFICECODE and CITY columns, drag to query text. Expected result: "CLASSICMODELS.OFFICES.OFFICECODE,CLASSICMODELS.OFFICES.CITY" is inserted in query text. Actual result: "null,CLASSICMODELS.OFFICES.OFFICECODE,CLASSICMODELS.OFFICES.CITY" is inserted
data/org.eclipse.birt.report.data.oda.jdbc.ui/src/org/eclipse/birt/report/data/oda/jdbc/ui/editors/SQLDataSetEditorPage.java
{
					if ( items[i].getGrayed( ) )
					{
						availableDbObjectsTree.setRedraw( false );
						availableDbObjectsTree.deselectAll( );
						availableDbObjectsTree.setRedraw( true );
						availableDbObjectsTree.redraw( );
					}
				}
			}
		} );
		
		
		Group selectTableGroup = new Group( tablescomposite, SWT.FILL );
		{
			GridLayout groupLayout = new GridLayout( );
			groupLayout.numColumns = 3;
			
			groupLayout.verticalSpacing = 10;
			selectTableGroup.setLayout( groupLayout );
			GridData data = new GridData( GridData.FILL_HORIZONTAL );
			selectTableGroup.setLayoutData( data );
		}
		schemaLabel = new Label( selectTableGroup, SWT.LEFT );
		schemaLabel.setText( JdbcPlugin.getResourceString( "tablepage.label.schema" ) );
		schemaCombo = new Combo( selectTableGroup, SWT.READ_ONLY );
		GridData gd = new GridData( GridData.FILL_HORIZONTAL );
		gd.horizontalSpan = 2;
		schemaCombo.setLayoutData( gd );
		enableSchemaComponent( isSchemaSupported );