init gpu buffer at program start with empty pendulum array

src/GLWidget.cpp

@@ -29,6 +29,9 @@ void GLWidget::initializeGL() {
 	glGenBuffers(1, &positionVBO);
 	glGenBuffers(1, &colorVBO);
 	glGenBuffers(1, &EBO);
+
+	std::vector<Pendulum*> empty;
+	initGPUMemory(&empty);
 }
 
 void GLWidget::paintGL() {