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
else if ( ( displayTextParam = ParameterAccessor
								.isDisplayText( paramName ) ) != null )
						{
							paramName = getParameterName( displayTextParam );
							if ( paramName != null )
							{
								if ( this.displayTexts == null )
									this.displayTexts = new HashMap( );
								this.displayTexts.put( paramName, paramValue );
							}
							continue;
						}
						
						paramName = getParameterName( paramName );
						ScalarParameterHandle parameter = (ScalarParameterHandle) findParameter( paramName );
						
						
						if ( paramValue != null && parameter != null )
						{
							try
							{
								if ( !DesignChoiceConstants.PARAM_TYPE_STRING
										.equalsIgnoreCase( parameter
												.getDataType( ) ) )
								{
									Object paramValueObj = ParameterValidationUtil
											.validate(
													parameter.getDataType( ),
													parameter.getPattern( ),
													paramValue, ULocale.US );