*: use NULL for null pointers

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
diff --git a/e2fsprogs/old_e2fsprogs/ext2fs/namei.c b/e2fsprogs/old_e2fsprogs/ext2fs/namei.c
index 4d4e378..14d48fb 100644
--- a/e2fsprogs/old_e2fsprogs/ext2fs/namei.c
+++ b/e2fsprogs/old_e2fsprogs/ext2fs/namei.c
@@ -30,7 +30,7 @@
 			     char *buf, ext2_ino_t *res_inode)
 {
 	char *pathname;
-	char *buffer = 0;
+	char *buffer = NULL;
 	errcode_t retval;
 	struct ext2_inode ei;