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/i18n/ResourceConstants.java
public final static String METADATA_NOT_AVAILABLE = "data.engine.NoResultMetadata";
	public final static String QUERY_HAS_PREPARED = "data.engine.QueryAlreadyPrepared";
	public final static String QUERY_HAS_NOT_PREPARED = "data.engine.QueryNotPrepared";
	public final static String INAVLID_FIELD_NAME = "data.engine.InvalidFieldName";
	public final static String DUPLICATE_COLUMN_NAME = "data.engine.DupColumnName";
	public final static String DUPLICATE_ALIAS_NAME = "data.engine.DupAlias";
	public final static String INVALID_FIELD_INDEX = "data.engine.InvalidFieldIndex";
	
	public final static String MATCH_ERROR = "data.engine.MatchError";
	public final static String UNSUPPORTED_DATA_TYPE = "data.engine.BadOperandType";
	
	public final static String BAD_PARAM_COUNT = "data.engine.BadParameterCount";
	public final static String BAD_PARAM_TYPE = "data.engine.BadParameterType";
	public final static String NO_SOLUTION_FOUND = "data.engine.NoIrrSolution";
	public final static String EXPECT_BOOLEAN_RETURN_TYPE = "data.engine.BadFetchScriptReturnType";
	public final static String BAD_INTERVAL_UNIT = "data.engine.BadIntervalUnit";
	public final static String INVALID_FIELD_NAME = "data.engine.InvalidFieldName";
	public final static String BAD_GROUP_KEY_TYPE = "data.engine.BadGroupKeyType";
	public final static String BAD_GROUP_INTERVAL_TYPE = "data.engine.group.interval";
	public final static String BAD_GROUP_INTERVAL_TYPE_ROWID = "data.engine.group.interval.Rowid";
	public final static String UNSUPPORTED_FILTER_ON_GROUP="data.engine.NoSupportFilterOnGroup";
	public final static String INVALID_TOP_BOTTOM_ARGUMENT="data.engine.InvalidTopBottomArgument";
	public final static String INVALID_TOP_BOTTOM_N_ARGUMENT="data.engine.InvalidTopBottomNArgument";
	public final static String INVALID_TOP_BOTTOM_PERCENT_ARGUMENT="data.engine.InvalidTopBottomPercentArgument";
	public final static String ILLEGAL_PARAMETER_FUN = "data.engine.BadAggrFuncParam";
	public final static String RESET_RATE = "data.engine.ResetRateGuess";
	public final static String UNSUPPORTTED_COND_OPERATOR = "data.engine.UnsupportedCondOp";
	public final static String EXPRESSION_CANNOT_BE_NULL_OR_BLANK = "data.engine.EmptyExpression";	
	public final static String GROUP_FILTERING_IS_NOT_ALLOWED_IN_GIVEN_QUERY="data.engine.GroupFilteringIsNotAllowedInGiverQuery";