Fix NPE in OAuth2 failure handler

application/src/main/java/org/thingsboard/server/service/security/auth/oauth2/Oauth2AuthenticationFailureHandler.java

@@ -54,8 +54,11 @@ public class Oauth2AuthenticationFailureHandler extends SimpleUrlAuthenticationF
             throws IOException, ServletException {
         String baseUrl;
         String errorPrefix;
+        String callbackUrlScheme = null;
         OAuth2AuthorizationRequest authorizationRequest = httpCookieOAuth2AuthorizationRequestRepository.loadAuthorizationRequest(request);
-        String callbackUrlScheme = authorizationRequest.getAttribute(TbOAuth2ParameterNames.CALLBACK_URL_SCHEME);
+        if (authorizationRequest != null) {
+            callbackUrlScheme = authorizationRequest.getAttribute(TbOAuth2ParameterNames.CALLBACK_URL_SCHEME);
+        }
         if (!StringUtils.isEmpty(callbackUrlScheme)) {
             baseUrl = callbackUrlScheme + ":";
             errorPrefix = "/?error=";