Remove bug that inhibited POST cache to shrink

scheme/httpd/surflets/bindings.scm

@@ -5,7 +5,7 @@
 ;; a later GET-BINDINGS call on the same POST request. The requests
 ;; are referenced by a weak pointer. Thread-safe as all threads use
 ;; the same lock.
-(define *POST-bindings-cache* '())
+(define *POST-bindings-cache* '(#f))
 (define *cache-lock* (make-lock))
 
 (define (get-bindings surflet-request)
@@ -55,18 +55,19 @@
   (obtain-lock *cache-lock*)
   (let ((result 
 	 (let loop ((cache *POST-bindings-cache*))
-	   (if (null? cache)
+	   (let ((tail (cdr cache)))
+	     (if (null? tail)	; cache has at least one element
 		 #f			; no such request cached
-	       (let* ((head (car cache))
+		 (let* ((head (car tail))
 			(s-req (weak-pointer-ref (car head))))
 		   (if s-req
 		       (if (eq? s-req surflet-request)
 			   (cdr head)	; request is cached
 			   (loop (cdr cache))) ; request isn't cached
-		     (begin
-		       ;; request object is gone ==> remove it from list
-		       (set! cache (cdr cache))
-		       (loop cache))))))))
+		       (begin     ;; request object is gone ==> remove
+			 ;; it from list
+			 (set-cdr! cache (cdr tail))
+			 (loop cache)))))))))
     (release-lock *cache-lock*)
     result))