Server crash due to invalid HTTP-version when trying to convert string to float

How to recreate crash

Sending a HTTP GET-request with an invalid HTTP-version such as a string, will cause the server to crash due to an invalid argument. The example below demonstrates this:

telnet localhost 8080
GET / HTTP/hei

Backtrace

terminate called after throwing an instance of 'std::invalid_argument'
 what():  stof

Program received signal SIGABRT, Aborted.
__GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
51	../sysdeps/unix/sysv/linux/raise.c: No such file or directory.
(gdb) bt
#0  __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:51
#1  0x00007ffff705f801 in __GI_abort () at abort.c:79
#2  0x00007ffff76b4957 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#3  0x00007ffff76baae6 in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#4  0x00007ffff76bab21 in std::terminate() ()
  from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#5  0x00007ffff76bad54 in __cxa_throw ()
  from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#6  0x00007ffff76b67eb in ?? () from /usr/lib/x86_64-linux-gnu/libstdc++.so.6
#7  0x00005555556625b3 in __gnu_cxx::__stoa<float, float, char> (
   __convf=0x7ffff7064fc0 <__GI_strtof>, __name=0x5555556b3036 "stof", 
   __str=0x5555558fccd0 "hei", __idx=0x0)
   at /usr/include/c++/7/ext/string_conversions.h:83
#8  0x0000555555655a5a in std::__cxx11::stof (__str="hei", __idx=0x0)
   at /usr/include/c++/7/bits/basic_string.h:6398
#9  0x000055555566f55f in SimpleWeb::ServerBase<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> > >::write(std::shared_ptr<SimpleWeb::ServerBase<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> > >::Session> const&, std::function<void (std::shared_ptr<SimpleWeb::ServerBase<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> > >::Response>, std::shared_ptr<SimpleWeb::ServerBase<boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::strea---Type <return> to continue, or q <return> to quit---Quit