CLI: Allow no music to be played if save pos used

If you provided any one of -playx, -playy, -playrx, -playry, -playgc, or
-playmusic in command-line arguments for command-line playtesting, then
the game would always try to play music, even if you passed a negative
-playmusic. This wouldn't do anything in that case, unless you had
MMMMMM installed, in which case it would play MMMMMM track 15
(Predestined Fate Final Level) due to the legacy wraparound bug.

To fix this, only play music if the track provided is greater than -1.
Additionally, to prevent it from playing Path Complete by default if you
specify any of the other save position arguments but n ot -playmusic,
it's now initialized to -1 instead of 0.

desktop_version/src/Game.cpp

@@ -5387,7 +5387,10 @@ void Game::customloadquick(const std::string& savfile)
         saverx = playrx;
         savery = playry;
         savegc = playgc;
-        music.play(playmusic);
+        if (playmusic > -1)
+        {
+            music.play(playmusic);
+        }
         return;
     }