lua: unpack treats explicit nil i/j as missing (defaults to 1 and #t)

lib/lua/runtime.sx

@@ -1552,23 +1552,25 @@
 (define
   lua-unpack
   (fn (&rest args)
-    (let ((t (first args))
-          (i (if (> (len args) 1) (nth args 1) 1))
-          (j (if (> (len args) 2) (nth args 2) (lua-len (first args)))))
-      (cond
-        ((> i j) nil)
-        (else
-          (let ((out (list (quote lua-multi))))
-            (begin
-              (define
-                loop
-                (fn (k)
-                  (when (<= k j)
-                    (begin
-                      (set! out (append out (list (get t (str k)))))
-                      (loop (+ k 1))))))
-              (loop i)
-              out)))))))
+    (let ((t (first args)))
+      (let ((i-raw (if (> (len args) 1) (nth args 1) nil))
+            (j-raw (if (> (len args) 2) (nth args 2) nil)))
+        (let ((i (if (= i-raw nil) 1 i-raw))
+              (j (if (= j-raw nil) (lua-len t) j-raw)))
+          (cond
+            ((> i j) nil)
+            (else
+              (let ((out (list (quote lua-multi))))
+                (begin
+                  (define
+                    loop
+                    (fn (k)
+                      (when (<= k j)
+                        (begin
+                          (set! out (append out (list (get t (str k)))))
+                          (loop (+ k 1))))))
+                  (loop i)
+                  out)))))))))
 
 (define
   lua-table-maxn