graphviz.ffi: use unless-zero.

diff --git a/extra/graphviz/ffi/ffi.factor b/extra/graphviz/ffi/ffi.factor
index f5b7e1bc710b99cec605d8df3a92603c15004824..23865e2eacb554e67afc6166e5f4a55ce35e59ad 100644 (file)
--- a/extra/graphviz/ffi/ffi.factor
+++ b/extra/graphviz/ffi/ffi.factor
@@ -105,7 +105,7 @@ M: ffi-errors error.
     "(The messages were probably printed to STDERR.)" print ;
 
 : gvFreeContext ( gvc -- )
-    int-gvFreeContext [ ] [ ffi-errors ] if-zero ;
+    int-gvFreeContext [ ffi-errors ] unless-zero ;
 
 DESTRUCTOR: gvFreeContext