Observe cider-stacktrace-print-level for test errors.

Pass the `cider-stacktrace-print-level` defcustom added in 2142ee5 when viewing
stacktraces for test errors.

Also, change `if` to a `when` to clarify intent.

Author: jeffvalk

cider-interaction.el

@@ -1041,8 +1041,8 @@ They exist for compatibility with `next-error'."
     (nrepl-send-request
      (append
       (list "op" "stacktrace" "session" session)
-      (if cider-stacktrace-print-level
-          (list "print-level" cider-stacktrace-print-level)))
+      (when cider-stacktrace-print-level
+        (list "print-level" cider-stacktrace-print-level)))
      (lambda (response)
        (nrepl-dbind-response response (class status)
          (cond (class  (setq causes (cons response causes)))

cider-test.el

@@ -172,8 +172,11 @@
   "Display stacktrace for the erring NS VAR test with the assertion INDEX."
   (let (causes)
     (nrepl-send-request
-     (list "op" "test-stacktrace" "session" (nrepl-current-session)
-           "ns" ns "var" var "index" index)
+     (append
+      (list "op" "test-stacktrace" "session" (nrepl-current-session)
+            "ns" ns "var" var "index" index)
+      (when cider-stacktrace-print-level
+        (list "print-level" cider-stacktrace-print-level)))
      (lambda (response)
        (nrepl-dbind-response response (class status)
          (cond (class  (setq causes (cons response causes)))