Resolves possible null reference

FitConnect/Router.cs

@@ -56,7 +56,7 @@ public class Router : IRouter {
 
             if (!verifyJwt) {
                 throw new Exception(
-                    $"SubmissionHost does not match DesitnationParamters SubmissionUrl");
+                    $"SubmissionHost does not match DestinationParameters SubmissionUrl");
             }
         }
 
@@ -70,7 +70,8 @@ public class Router : IRouter {
                 Base64UrlEncoder.Decode(signature.EncodedPayload));
 
         string? submissionHost = payload?.submissionHost;
-        return route.DestinationParameters.SubmissionUrl.EndsWith(submissionHost);
+        return submissionHost != null &&
+               route.DestinationParameters.SubmissionUrl.EndsWith(submissionHost);
     }
 
     private async Task<bool> VerifyDestinationParametersSignature(Route route) {