Oops. Fix bad initialization of the "seen" array, causing us to not

properly clear the reference count at init time. It happened to work
for me by pure luck.

Until it broke, and my unreferenced commit suddenly looked referenced
again. Fixed.

fsck-cache.c

@@ -106,7 +106,7 @@ static int mark_sha1_seen(unsigned char *sha1, char *tag)
 		seen = realloc(seen, alloc_seen*sizeof(struct seen));
 	}
 	s = seen + nr_seen;
-	memset(s, 0, sizeof(s));
+	memset(s, 0, sizeof(*s));
 	nr_seen++;
 	memcpy(s->sha1, sha1, 20);
 	strncpy(s->tag, tag, sizeof(s->tag));