No, the problem comes from the assumption that you can legally fetch the "address" of a structure member via pointer dereference without checking for null so long as you don't actually try to access the resulting address.

    struct usb_line6 *line6 = &podhd->line6;

The assumption is that this is OK so long as you don't try to access the contents of line6 without doing some upstream null checking first. This assumption is false. The very act of dereferencing is undefined, regardless of whether you access the resulting address or not.

The assumption fails whether null is implemented as 0, 200, 0x8000000000000000, 0xffffffffffffffff.