sam: fix spurious overwrite message

Fixes:

% sam -d
 -.
w foo
foo: (new file) #0
w foo
?warning: write might change good version of `foo'

1 files changed, 1 insertions, 1 deletions

diff --git a/src/cmd/sam/io.c b/src/cmd/sam/io.c
index c112c0a1..c3dc9778 100644
--- a/src/cmd/sam/io.c
+++ b/src/cmd/sam/io.c
@@ -63,7 +63,7 @@ writef(File *f)
 		warn(Wnotnewline);
 	closeio(n);
 	if(f->name.s[0]==0 || samename){
-		if(statfile(name, &dev, &qid, &mtime, 0, 0) > 0){
+		if(statfile(genc, &dev, &qid, &mtime, 0, 0) > 0){
 			f->dev = dev;
 			f->qidpath = qid;
 			f->mtime = mtime;