Bug 153506 Strange error message when group key refers to bad binding column name
Run attached report design. The following error is shown: Group key "groupkey" in group 1 cannot depend on column bindings defined in the group lower than itself. This is a strange error. Since the actual problem is that the table's binding column "groupkey" is defined to refer to another existing binding: row["bad"]. EXPECTED BEHAVIOR: The error message should clearly indicate that a non-existing binding is the cause of the failure.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ExprManagerUtil.java
throws DataException
	{
		ExprManagerUtil util = new ExprManagerUtil( );
		
		util.exprManager = exprManager;
		util.checkDependencyCycle( ); 
		util.checkGroupNameValidation( );
	}
	/**
	 *	Test whether high level group keys are depended on low level group keys.
	 * 
	 * @param exprManager
	 * @return
	 * @throws DataException 
	 */
	private void checkGroupNameValidation( ) throws DataException
	{
		HashMap map = this.getGroupKeys( );
		Iterator it = map.keySet( ).iterator( );
		while ( it.hasNext( ) )
		{
			Integer level = (Integer)it.next( );
			exprManager.setEntryGroupLevel( level.intValue( ) );
			
			if(!ExpressionCompilerUtil.hasColumnRow( map.get( level ).toString( ), exprManager ))
			{
				exprManager.setEntryGroupLevel( ExprManager.OVERALL_GROUP );
				if( !isColumnBindingExist(map.get( level ).toString( ) ))
				{
					throw new DataException( ResourceConstants.COLUMN_BINDING_NOT_EXIST, map.get( level ).toString( ));