SpringBoot fix FreeMarkerConfigurer(xml) check template path error in fatjar

If bean freeMarkerConfigurer created by xml, afterProperitesSet will throw an error ,the spring debug the exception by try...catch this update avoid the error.

java.io.FileNotFoundException: ServletContext resource [/] cannot be resolved to absolute file path - web application archive not expanded?
    at org.springframework.web.util.WebUtils.getRealPath(WebUtils.java:344)
    at org.springframework.web.context.support.ServletContextResource.getFile(ServletContextResource.java:194)
    at org.springframework.ui.freemarker.FreeMarkerConfigurationFactory.getTemplateLoaderForPath(FreeMarkerConfigurationFactory.java:345)
    at org.springframework.ui.freemarker.FreeMarkerConfigurationFactory.createConfiguration(FreeMarkerConfigurationFactory.java:297)
    at org.springframework.web.servlet.view.freemarker.FreeMarkerConfigurer.afterPropertiesSet(FreeMarkerConfigurer.java:120)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1855)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1792)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:595)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517)
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:226)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202)
    at org.springframework.beans.factory.support.DefaultListableBeanFactory.preInstantiateSingletons(DefaultListableBeanFactory.java:893)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:879)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:551)
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:143)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:758)
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:750)
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1237)
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226)
    at com.mycompany.biz.TradeAppApplication.main(TradeAppApplication.java:46)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at org.springframework.boot.loader.MainMethodRunner.run(MainMethodRunner.java:49)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:109)
    at org.springframework.boot.loader.Launcher.launch(Launcher.java:58)
    at org.springframework.boot.loader.WarLauncher.main(WarLauncher.java:59)

Comment From: wilkinsona

Thanks for the pull request. Unfortunately, I don't understand the problem that it fixes. So that we can see the problem and verify that this pull request fixes it, can you please add one or more tests that fail without your changes to the main code and pass with those changes in place?