Bug 148951 Wrong error msg when set nonexisted col as group key
Description: Wrong error msg when set nonexisted col as group key Steps to reproduce: 1. Insert a table, bind it to dataset 2. Add a group, input abc as group key which is invalid. 3. Preview Expected result: Friendly error msg to tell user the group key is wrong. Actual result: + Group key "abc" in group 1 cannot depend on column bindings defined in the group lower than itself. data.engine.InvalidGroupKey ( 1 time(s) ) detail : org.eclipse.birt.data.engine.core.DataException: Group key "OUNTR" in group 1 cannot depend on column bindings defined in the group lower than itself.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/impl/ExprManagerUtil.java
if ( l != null )
				{
					for ( int j = 0; j < l.size( ); j++ )
					{
						n.addChild( new Node( l.get( j ) == null ? null
								: l.get( j ).toString( ) ) );
					}
				}
			}
			result.add( n );
		}
		Node[] source = new Node[result.size( )];
		for ( int i = 0; i < source.length; i++ )
		{
			source[i] = (Node) result.get( i );
		}
		validateNodes( source );
	}
	/**
	 * 
	 * @param source
	 * @return
	 * @throws DataException 
	 */
	private void validateNodes( Node[] source ) throws DataException
	{
		Node[] preparedNodes = populateNodeList( source );
		for ( int i = 0; i < preparedNodes.length; i++ )
		{
			isValidNode( preparedNodes[i], preparedNodes[i] );