removed a useless check in foreign-alloc

original commit: a629477f50dffd0cdc838276bbbf31f06504d958

LOG

@@ -582,3 +582,5 @@
   simplified test and finding the initial solution.
     cpnanopass.ss,
     3.ms
+- removed a useless check in foreign-alloc
+    record.ss

s/record.ss

@@ -51,10 +51,7 @@
         (lambda (n)
           (unless (and (fixnum? n) (fx> n 0))
             ($oops who "~s is not a positive fixnum" n))
-          (let ([x (malloc n)])
-            (if (string? x)
-                ($oops who "system call failed: ~(~a~)" x)
-                x)))))
+          (malloc n))))
 
     (set-who! foreign-free
       (let ([free (foreign-procedure "(cs)free" (uptr) void)])