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
{
			if ( nodes[i].equals( node ) )
				return nodes[i];
		}
		return null;
	}
	
	/**
	 * 
	 * @return
	 */
	private List getColumnNames( )
	{
		List bindingExprs = exprManager.getBindingExprs( );
		Map autoBindingExprMap = exprManager.getAutoBindingExprMap( );
		List l = new ArrayList( );
		l.addAll( autoBindingExprMap.keySet( ) );
		for ( int i = 0; i < bindingExprs.size( ); i++ )
		{
			l.addAll( ( (GroupBindingColumn) bindingExprs.get( i ) ).getColumnNames( ) );
		}
		return l;
	}
	
	/**
	 * 
	 * @return
	 */
	private HashMap getGroupKeys( )
	{