fixed isSessionValid api call

rest-api/src/main/java/lcsb/mapviewer/api/users/UserController.java

@@ -4,6 +4,7 @@ import java.io.IOException;
 import java.util.*;
 import java.util.stream.Collectors;
 
+import lcsb.mapviewer.common.Configuration;
 import org.apache.logging.log4j.LogManager;
 import org.apache.logging.log4j.Logger;
 import org.springframework.beans.factory.annotation.Autowired;
@@ -38,7 +39,7 @@ public class UserController extends BaseController {
    * whether the current session is still valid.
    */
   @GetMapping(value = "/isSessionValid")
-  @PreAuthorize("isAuthenticated()")
+  @PreAuthorize("isAuthenticated() and authentication.name != '" + Configuration.ANONYMOUS_LOGIN + "'")
   public Object isSessionValid(Authentication authentication) {
     return new TreeMap<>();
   }