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
reset( );
					return true;
				}
			}
			return false;
		}
		else
		{
			reset( );
			return false;
		}
	}
	/**
	 * Reset all the member data to their default value.
	 */
	private void reset( )
	{
		if ( firstPassRowNumberCounter  == secondPassRowNumberCounter )
		{
			doReset();
		}
	}
	/**
	 * 
	 *
	 */
	private void doReset()
	{
		firstPassRowNumberCounter = 0;
		secondPassRowNumberCounter = 0;