Fix Nullability

docs/src/test/kotlin/org/springframework/security/kt/docs/servlet/test/testmethod/HelloMessageService.kt

@@ -29,7 +29,7 @@ class HelloMessageService : MessageService {
 
 	@PreAuthorize("isAuthenticated()")
 	override fun getMessage(): String {
-		val authentication: Authentication = SecurityContextHolder.getContext().authentication
+		val authentication: Authentication? = SecurityContextHolder.getContext().authentication
 		return "Hello $authentication"
 	}
 

docs/src/test/kotlin/org/springframework/security/kt/docs/servlet/test/testmethodwithuserdetails/WithCustomUserDetailsTests.kt

@@ -47,7 +47,7 @@ class WithCustomUserDetailsTests {
     fun getMessageWithUserDetailsServiceBeanName() {
         val message: String = messageService.getMessage()
         assertThat(message).contains("customUsername");
-        val principal = SecurityContextHolder.getContext().authentication.principal
+        val principal = SecurityContextHolder.getContext().authentication!!.principal
         assertThat(principal).isInstanceOf(CustomUserDetails::class.java)
     }
     // end::custom-user-details-service[]