PenLayer: Allow setting engine without OpenGL context

Author: adazem009

src/penlayer.cpp

@@ -47,7 +47,7 @@ void PenLayer::setEngine(libscratchcpp::IEngine *newEngine)
 
     m_engine = newEngine;
 
-    if (m_engine) {
+    if (m_engine && QOpenGLContext::currentContext()) {
         m_projectPenLayers[m_engine] = this;
         m_fbo = std::make_unique<QOpenGLFramebufferObject>(m_engine->stageWidth(), m_engine->stageHeight(), m_fboFormat);
         Q_ASSERT(m_fbo->isValid());