fs/ntfs3: handle hdr_first_de() return value

In the Linux kernel, the following vulnerability has been resolved: 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.