mount: fix dereference after null check

CID 1168169 (#1 of 1): Dereference after null check (FORWARD_NULL)
7. var_deref_model: Passing "mi" to function "do_bind_mount(struct
   mount_info *)", which dereferences null "mi->bind"
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

mount.c

@@ -1305,7 +1305,7 @@ static int restore_ext_mount(struct mount_info *mi)
 
 static int do_bind_mount(struct mount_info *mi)
 {
-	bool shared = mi->shared_id && mi->shared_id == mi->bind->shared_id;
+	bool shared = 0;
 
 	if (!mi->need_plugin) {
 		char *root, rpath[PATH_MAX];
@@ -1322,6 +1322,8 @@ static int do_bind_mount(struct mount_info *mi)
 			goto do_bind;
 		}
 
+		shared = mi->shared_id && mi->shared_id == mi->bind->shared_id;
+
 		/*
 		 * Cut common part of root.
 		 * For non-root binds the source is always "/" (checked)