Bug 207250 Check blank value for datetime type parameter from url.[0002][0705]
Description: Check blank value for datetime type parameter from url. Build number:2.3.0.v20071023 Steps to reproduce: 1. New a datetime parameter mydt,listbox, tick off isRequired. 2. Preview in external browser and add "&dt=" in url, press enter. Expected result: Error message to indicate blank value isn't allowed for this parameter. Actual result: No error message and blank value is accepted. I tried to new a jsp and use <birt:paramDef> to pass the blank value and the blank value is accepted,too. Error log:n/a
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/context/ViewerAttributeBean.java
* Report parameters as string map
	 */
	private Map parametersAsString = null;
	/**
	 * Report parameter definitions List
	 */
	private Collection parameterDefList = null;
	/**
	 * Display Text of Select Parameters
	 */
	private Map displayTexts = null;
	/**
	 * Module Options
	 */
	private Map moduleOptions = null;
	/**
	 * Request Type
	 */
	private String requestType;
	/**
	 * Default parameter values map
	 */
	private Map defaultValues;
	/**
	 * Locale parameter list
	 */
	private List locParams;
	/**
	 * Constructor.
	 *