Update httplib.h

use std::exception_ptr

httplib.h

@@ -616,7 +616,7 @@ public:
   using Handler = std::function<void(const Request &, Response &)>;
 
   using ExceptionHandler =
-      std::function<void(const Request &, Response &, std::exception &e)>;
+      std::function<void(const Request &, Response &, std::exception_ptr &ep)>;
 
   enum class HandlerResponse {
     Handled,
@@ -5733,7 +5733,8 @@ Server::process_request(Stream &strm, bool close_connection,
     routed = routing(req, res, strm);
   } catch (std::exception &e) {
     if (exception_handler_) {
-      exception_handler_(req, res, e);
+      auto ep = std::current_exception();
+      exception_handler_(req, res, ep);
       routed = true;
     } else {
       res.status = 500;