Avoid unpausing music when debugger is toggled

Workaround a Flixel issue where sounds can unpause after toggling
the Flixel debugger with F2, caused by the debugger throwing a
spurious onFocus event without an onFocusLost event.

source/funkin/audio/FunkinSound.hx

@@ -90,6 +90,11 @@ class FunkinSound extends FlxSound implements ICloneable<FunkinSound>
    */
   var _label:String = "unknown";
 
+  /**
+   * Whether we received a focus lost event.
+   */
+  var _lostFocus:Bool = false;
+
   public function new()
   {
     super();
@@ -177,7 +182,10 @@ class FunkinSound extends FlxSound implements ICloneable<FunkinSound>
    */
   override function onFocus():Void
   {
-    if (!_alreadyPaused)
+    // Flixel can sometimes toss spurious `onFocus` events, e.g. if the Flixel debugger is toggled
+    // on and off. We only want to resume the sound if we actually lost focus, and if we weren't
+    // already paused before we lost focus.
+    if (_lostFocus && !_alreadyPaused)
     {
       resume();
     }
@@ -185,6 +193,7 @@ class FunkinSound extends FlxSound implements ICloneable<FunkinSound>
     {
       trace('Not resuming audio on focus!');
     }
+    _lostFocus = false;
   }
 
   /**
@@ -193,6 +202,7 @@ class FunkinSound extends FlxSound implements ICloneable<FunkinSound>
   override function onFocusLost():Void
   {
     trace('Focus lost, pausing audio!');
+    _lostFocus = true;
     _alreadyPaused = _paused;
     pause();
   }