fix user Service - no NPE if SecureContext is missing

pluto-server/src/main/java/de/itvsh/ozg/pluto/common/callcontext/CurrentUserService.java

@@ -36,12 +36,13 @@ public class CurrentUserService {
 		}
 	}
 
-	public Optional<Authentication> getAuthentication() {
+	public Optional<Authentication> findAuthentication() {
 		return findTrustedAuthentication();
 	}
 
 	Optional<Authentication> findTrustedAuthentication() {
-		return Optional.ofNullable(SecurityContextHolder.getContext().getAuthentication())
+		return Optional.ofNullable(SecurityContextHolder.getContext())
+				.map(context -> context.getAuthentication())
 				.filter(auth -> !trustResolver.isAnonymous(auth))
 				.filter(Authentication::isAuthenticated);
 	}