Bug 182673 No default value error message prompts incorrectly
Steps to reproduce: 1. New a report parameter; 2. Choose control type as Combo; 3. Choose parameter as dynamic type; Expected result: As the isRequired is false by default, parameter's default value can be null value. There should be no error message about no default value prompt. Actual result; Error messages prompts
UI/org.eclipse.birt.report.designer.ui/src/org/eclipse/birt/report/designer/ui/dialogs/ParameterDialog.java
}
	private String format( String string )
	{
		if ( canBeNull( ) && string == null )
		{
			return LABEL_NULL;
		}
		if ( StringUtil.isBlank( string ) || formatCategroy == null )
		{
			return string;
		}
		try
		{
			String pattern = formatPattern;
			if ( formatPattern == null )
			{
				if ( isCustom( ) )
				{
					return string;
				}
				pattern = formatCategroy;
			}
			if ( DesignChoiceConstants.PARAM_TYPE_DATETIME.equals( getSelectedDataType( ) ) )
			{
				Date date = DataTypeUtil.toDate( string, ULocale.US );
				DateFormatter formatter = new DateFormatter( pattern );
				string = formatter.format( date );
			}
			else if ( DesignChoiceConstants.PARAM_TYPE_FLOAT.equals( getSelectedDataType( ) ) )
			{