[Commits] [wesnoth/wesnoth] cf4788: Fix compatibility with boost 1.50

[GitHub]

  Branch: refs/heads/master
  Home:   https://github.com/wesnoth/wesnoth
  Commit: cf4788cc3a1a6a35a13f00f9d98e69a2466c7d15
      https://github.com/wesnoth/wesnoth/commit/cf4788cc3a1a6a35a13f00f9d98e69a2466c7d15
  Author: Alexander van Gessel <ai0867 at gmail.com>
  Date:   2017-10-30 (Mon, 30 Oct 2017)

  Changed paths:
    M src/scripting/lua_audio.cpp

  Log Message:
  -----------
  Fix compatibility with boost 1.50

boost::optional.value was added later, so use the get method instead.