Bug 124629 Use Top/Bottom n in a field containing null value inside will cause DataException.
Description: Use Top/Bottom n in a field containing null value inside will cause DataException. Steps to reproduce: 1. New a data source and dataset 2. Add a filter on a field, set operator to top 5 3. Click Preview Result. Result: A BIRT exception occurred. Plug-in Provider:Eclipse.org Plug-in Name:BIRT Data Engine Plug-in ID:org.eclipse.birt.data Version:2.0.0 Error Code:data.engine.DataConversionError Error Message:An error happened in data type conversion. Can not convert the value of {NULL_VALUE_!@#$%^&} to Double type.
data/org.eclipse.birt.data/src/org/eclipse/birt/data/engine/script/NEvaluator.java
{
			return doFirstPass( value );
		}
		else if ( filterPassController.getPassLevel( ) == FilterPassController.SECOND_PASS )
		{
			return doSecondPass( );
		}
		return false;
	}
	/**
	 * Do the first pass. In the first pass we maintain a value list and a row id list that will
	 * host all top/bottom N values/rowIds so that in pass 2 we can use them to filter rows out.
	 * @param value
	 * @return
	 * @throws DataException
	 */
	private boolean doFirstPass( Object value ) throws DataException
	{
		firstPassRowNumberCounter++;
		if ( valueList == null )
		{
			valueList = new Object[N];
			rowIdList = new int[N];
		}
		populateValueListAndRowIdList( value, N );
		return true;
	}
	/**
	 * @param value
	 * @param N