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
* Whether should the DatabaseObjectTree should be expanded.
	 * 
	 * @param expand True if the expanding is expected. Otherwise false.
	 */
	public void setDatabaseObjectTreeExpansion( boolean expand )
	{
		this.expandDbObjectsTree = expand;
	}
	
	/**
	 * remove the tree item's direct child treeItem, cause since 3.1,
	 * TreeItem.removeAll is supported.But in 3.0,this method is not supported.
	 * 
	 * @param treeItem
	 */
	private void removeTreeItem( TreeItem treeItem )
	{
		if ( treeItem.isDisposed( ) )
			return;
		TreeItem[] items = treeItem.getItems( );
		for ( int i = 0; i < items.length; i++ )
		{
			if ( items[i] != null && !items[i].isDisposed( ) )
			{
				items[i].dispose( );
			}
		}
	}
}
class DbType