Comment 4 for bug 1533495

We see a different exception in the latter core:

(gdb) p what
$1 = {static npos = <optimized out>, _M_dataplus = {<std::allocator<char>> = {<__gnu_cxx::new_allocator<char>> = {<No data fields>}, <No data fields>},
    _M_p = 0x7f96980129c8 "basic_string::_S_construct null not valid"}}