Bug 153412 Change parameter type will cause preview fail
Description: Change parameter type will cause preview fail Steps to reproduce: 1. New a report paramter, string, text-box, default value is abc. 2. Drag the parameter to Layout and preview. 3. Change the parameter's type to integer, list-box, add a value 1 4. Preview Expected result: No errors. Actual result: The value "abc" is invalid with the type "integer".
viewer/org.eclipse.birt.report.viewer/birt/WEB-INF/classes/org/eclipse/birt/report/context/ViewerAttributeBean.java
String title = reportTitle;
		if ( reportDesignHandle != null )
		{
			Object design = reportDesignHandle.getDesignObject( );
			if ( design instanceof IReportRunnable )
			{
				IReportRunnable runnable = (IReportRunnable) design;
				String designTitle = (String) runnable
						.getProperty( IReportRunnable.TITLE );
				if ( designTitle != null && designTitle.trim( ).length( ) > 0 )
					title = designTitle;
			}
		}
		return title;
	}
	/**
	 * Get Display Text of select parameters
	 * 
	 * @param request
	 * @return Map
	 */
	protected Map getDisplayTexts( Map displayTexts, HttpServletRequest request )
	{
		if ( displayTexts == null )
			displayTexts = new HashMap( );
		Enumeration params = request.getParameterNames( );
		while ( params != null && params.hasMoreElements( ) )
		{
			String param = DataUtil.getString( params.nextElement( ) );
			String paramName = ParameterAccessor.isDisplayText( param );