try to fix iOS black frames recording

engine/app.cpp

@@ -354,7 +354,11 @@ void App::update(float dt)
             rec_timer = 0.f;
             
             auto data = new uint8_t[width * height * 4];
-            glBindFramebuffer(GL_READ_FRAMEBUFFER, 0);
+            #if __IOS__
+                [ios_view->glview bindDrawable];
+            #else
+                glBindFramebuffer(GL_FRAMEBUFFER, 0);
+            #endif
             glReadBuffer(GL_BACK);
             glReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, data);
             {