curl: heap-use-after-free in state.referer when CURLOPT_REFERER replaced or cleared after perform

Calling curleasysetoptcurl, CURLOPTREFERER, ... to replace or clear a previously-set referer after curleasyperform frees the old string via Curlsetstropt lib/setopt.c:87 but leaves data-state.referer.ptr pointing at the freed heap region. curleasygetinfoCURLINFOREFERER and curleasyduphandle then...