Fix use-after-free in ziptool.

Found by Hanno Böck <hanno@hboeck.de> using american fuzzy lop.

src/ziptool.c

diff --git a/src/ziptool.c b/src/ziptool.c
index b6a08ab..a0f4be4 100644
--- a/src/ziptool.c
+++ b/src/ziptool.c
@@ -208,8 +208,8 @@
 	}
     }
     if (n == -1) {
-	zip_fclose(zf);
 	fprintf(stderr, "can't read file at index '%" PRIu64 "': %s\n", idx, zip_file_strerror(zf));
+	zip_fclose(zf);
 	return -1;
     }
     if ((err = zip_fclose(zf)) != 0) {