receiver: should not call normalize if source/target is nil

if source or target is nil, it would not return an error message but
will throw an uncaught exception

java.lang.NullPointerException: Cannot invoke "String.length()" because
"this.input" is null

this is fixed by nil-guarding normalize function call

1 files changed, 4 insertions, 2 deletions

diff --git a/src/weepinbell/webserver/receiver.clj b/src/weepinbell/webserver/receiver.clj
index 9d14a10..1a34f8c 100644
--- a/src/weepinbell/webserver/receiver.clj
+++ b/src/weepinbell/webserver/receiver.clj
@@ -36,8 +36,10 @@
   Return JSON response of pending notification, rejection or error."
   [wm wmc config]
   (let [{:keys [s t]} wm
-        source (normalize s)
-        target (normalize t)
+        ;; if params are nil, use empty string 
+        ;; empty strings will fail check-request
+        source (if s (normalize s) "")
+        target (if t (normalize t) "")
         new-wm {:s source :t target}
         allowlist (:allowed-target-domains config)]
      ;; Request verification