code from my list class thats causing this error

Exception thrown: read access violation.

$**$this$**$ was nullptr.

Iterator begin$()$ const noexcept

$\{$

return Iterator$($fHead$,$ fTail$)$;

$\}$

Iterator end$()$ const noexcept

$\{$

return Iterator$($nullptr$,$ nullptr$)$;

$\}$

Iterator rbegin$()$ const noexcept

$\{$

return Iterator$($fTail$,$ fHead$)$;

$\}$

Iterator rend$()$ const noexcept

$\{$

return Iterator$($nullptr$,$ nullptr$)$;

$\}$

the bit of code that it is referencing

Iterator begin$()$ const noexcept

$\{$

return $++($rend$())$;

$\}$

Iterator end$()$ const noexcept

$\{$

Iterator iter $=*$this;

iter.fCurrent $=$ nullptr;

iter.fState $=$ States::AFTER;

return iter;

$\}$

Iterator rbegin$()$ const noexcept

$\{$

return $--($end$())$;

$\}$

Iterator rend$()$ const noexcept

$\{$

Iterator iter $=*$this;

iter.fCurrent $=$ nullptr;

iter.fState $=$ States::BEFORE;

return iter;

$\}$

fix