Fix filter set Authentication

src/main/java/eu/dnetlib/uoaauthorizationlibrary/security/AuthorizationFilter.java

@@ -27,7 +27,7 @@ public class AuthorizationFilter implements Filter {
     @Override
     public void doFilter(ServletRequest req, ServletResponse res, FilterChain filterChain) throws IOException, ServletException {
         OpenAIREAuthentication auth = authorizationProvider.getAuthentication((HttpServletRequest) req);
-        if(auth != null) {
+        if(auth.isAuthenticated()) {
             SecurityContextHolder.getContext().setAuthentication(auth);
         }
         filterChain.doFilter(req, res);