add check for eventListenerCount

src/components/inputManager.js

@@ -22,12 +22,12 @@ define(['playbackManager', 'focusManager', 'appRouter', 'dom'], function (playba
 
     var eventListenerCount = 0;
     function on(scope, fn) {
-        eventListenerCount++;
+        if (eventListenerCount) eventListenerCount++;
         dom.addEventListener(scope, 'command', fn, {});
     }
 
     function off(scope, fn) {
-        eventListenerCount--;
+        if (eventListenerCount) eventListenerCount--;
         dom.removeEventListener(scope, 'command', fn, {});
     }
 
@@ -234,4 +234,4 @@ define(['playbackManager', 'focusManager', 'appRouter', 'dom'], function (playba
         on: on,
         off: off
     };
-});
+});