fix vr controllers interfering with screen drawing

src/app.h

@@ -132,6 +132,7 @@ public:
     std::string doc_filename;
     bool has_stylus = false;
     bool has_vr = false;
+    bool vr_controllers_enabled = true;
     float off_x = 0;
     float off_y = 0;
     float width;