loader/efi/linux: Reset freed pointer

Avoid dangling pointer. Code should not be reached but better safe than sorry.

Signed-off-by: Frediano Ziglio <frediano.ziglio@cloud.com>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>

grub-core/loader/efi/linux.c

@@ -241,6 +241,7 @@ grub_arch_efi_linux_boot_image (grub_addr_t addr, grub_size_t size, char *args)
   grub_error (GRUB_ERR_BAD_OS, "start_image() returned 0x%" PRIxGRUB_EFI_UINTN_T, status);
   grub_efi_free_pages ((grub_addr_t) loaded_image->load_options,
 		       GRUB_EFI_BYTES_TO_PAGES (len));
+  loaded_image->load_options = NULL;
 unload:
   b->unload_image (image_handle);