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
case DbType.VIEW_TYPE:
					type = DbType.VIEW_STRING;
					break;
				case DbType.PROCEDURE_TYPE:
					type = DbType.PROCEDURE_STRING;
					break;
			}
		}
		
		return type;
	}
	/**
	* @param item A tree Item which has to be tested
	* @return if the TreeItem represents a Schema node
	*/
	protected boolean isSchemaNode( TreeItem item )
	{
		if ( item != null && isSchemaSupported )
		{
			if (item.getParentItem() == rootNode)
			{
				return true;
			}
		}
		return false;
	}
	
	/**
	 * refresh page
	 *