The data pointer in ngx_open_file_t objects must be initialized.

Uninitialized pointer may result in arbitrary segfaults if access_log is used
without buffer and without variables in file path.

Patch by Tatsuhiko Kubo (ticket #268).

src/core/ngx_conf_file.c

diff --git a/src/core/ngx_conf_file.c b/src/core/ngx_conf_file.c
index 0eb6388..ed7a2ce 100644
--- a/src/core/ngx_conf_file.c
+++ b/src/core/ngx_conf_file.c
@@ -946,6 +946,7 @@
     }
 
     file->flush = NULL;
+    file->data = NULL;
 
     return file;
 }