Bug 160184 [API]DataSetID.toString() should return null but return "null"
Description: DataSetID.toString() should return null but return "null" Steps to reproduce: Run below codes: new DataSetID( null, 0, null ).toString(); Expected result: null. Actual result: "null"
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/api/DataSetID.java
{
	DataSetID parent;
	long rowId;
	String queryName;
	String dataSetName;
	public DataSetID( DataSetID parent, long rowId, String queryName )
	{
		this.parent = parent;
		this.rowId = rowId;
		this.queryName = queryName;
	}
	public DataSetID getParentID( )
	{
		return parent;
	}
	public String getDataSetName( )
	{
		return dataSetName;
	}
	public String getQueryName( )
	{
		return queryName;
	}