js-on-sx: new <non-callable> throws TypeError instead of hanging

new (new Object("")) hung because js-new-call called
js-get-ctor-proto -> js-ctor-id -> inspect, and inspect on a
wrapper-with-proto-chain recurses through the prototype's
lambdas forever. Added (js-function? ctor) precheck at the top
of js-new-call that raises a TypeError instance instead.
conformance.sh: 148/148.

lib/js/runtime.sx

@@ -683,18 +683,22 @@
   js-new-call
   (fn
     (ctor args)
-    (let
-      ((obj (dict)))
-      (begin
-        (dict-set! obj "__proto__" (js-get-ctor-proto ctor))
+    (cond
+      ((not (js-function? ctor))
+        (raise (js-new-call TypeError (list (str (type-of ctor) " is not a constructor")))))
+      (else
         (let
-          ((ret (js-call-with-this obj ctor args)))
-          (if
-            (and
-              (not (js-undefined? ret))
-              (or (= (type-of ret) "dict") (= (type-of ret) "list") (js-function? ret)))
-            ret
-            obj))))))
+          ((obj (dict)))
+          (begin
+            (dict-set! obj "__proto__" (js-get-ctor-proto ctor))
+            (let
+              ((ret (js-call-with-this obj ctor args)))
+              (if
+                (and
+                  (not (js-undefined? ret))
+                  (or (= (type-of ret) "dict") (= (type-of ret) "list") (js-function? ret)))
+                ret
+                obj))))))))
 
 ;; Setter — mutates the dict. Returns the new value (JS assignment yields rhs).
 (define