Autoconfigure FreemarkerServletWebConfiguration conditional on FreemarkerViewResolver

Fixes problem where if Freemarker is present, but spring-webmvc isn't
present, then Spring Boot Autoconfigure will fail with ClassNotFoundException

Author: candrews

spring-boot-project/spring-boot-autoconfigure/src/main/java/org/springframework/boot/autoconfigure/freemarker/FreeMarkerServletWebConfiguration.java

@@ -43,7 +43,7 @@
  */
 @Configuration(proxyBeanMethods = false)
 @ConditionalOnWebApplication(type = ConditionalOnWebApplication.Type.SERVLET)
-@ConditionalOnClass({ Servlet.class, FreeMarkerConfigurer.class })
+@ConditionalOnClass({ Servlet.class, FreeMarkerConfigurer.class, FreeMarkerViewResolver.class })
 @AutoConfigureAfter(WebMvcAutoConfiguration.class)
 class FreeMarkerServletWebConfiguration extends AbstractFreeMarkerConfiguration {