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
*/
	private void checkDependencyCycle( ) throws DataException
	{
		List result = new ArrayList( );
		Iterator it = this.getColumnNames( ).iterator( );
		while ( it.hasNext( ) )
		{
			String name = it.next( ).toString( );
			Node n = new Node( name );
			IBaseExpression expr = exprManager.getExpr( name );
			if ( expr != null )
			{
				if ( !( expr instanceof IScriptExpression || expr instanceof IConditionalExpression ) )
				{
					throw new DataException( ResourceConstants.BAD_DATA_EXPRESSION );
				}
				List l = null;
				try
				{
					if ( expr instanceof IScriptExpression )
						l = ExpressionParserUtil.extractColumnExpression( (IScriptExpression) expr );
					else if ( expr instanceof IConditionalExpression )
						l = ExpressionParserUtil.extractColumnExpression( (IConditionalExpression) expr );
				}
				catch ( DataException e )
				{
					
					
				}