Make sure the replay is stopped if the main menu is opened (fixes #95)

src/main/java/com/replaymod/replay/ReplayModReplay.java

@@ -195,6 +195,10 @@ public class ReplayModReplay {
         replayHandler = new ReplayHandler(replayFile, true);
     }
 
+    public void forcefullyStopReplay() {
+        replayHandler = null;
+    }
+
     public ReplayMod getCore() {
         return core;
     }