fs/ntfs3: handle hdr_first_de() return value

The hdr_first_de() function returns a pointer to a struct NTFS_DE. This
pointer may be NULL. To handle the NULL error effectively, it is important
to implement an error handler. This will help manage potential errors
consistently.

Additionally, error handling for the return value already exists at other
points where this function is called.

Found by Linux Verification Center (linuxtesting.org) with SVACE.

Fixes: 82cae269 ("fs/ntfs3: Add initialization of super block")
Signed-off-by: Andrey Vatoropin <a.vatoropin@crpt.ru>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>