Can't track nodes when loading scene on app startup

[chnoblouch]

Nodes cannot be tracked by AppDemoVideo if the scene was loaded on app startup. It does work if the app loaded another scene first and the user afterwards switched to the tracking scene. However, if the tracked node is a camera, the tracking is functional.

[chnoblouch]

Possible cause: My camera isn't calibrated, so the calibration can't be loaded. This leads to a camera FOV of zero, which seems to corrupt further calculations (example: the normals of all the frustum planes are NaN, which disrupts frustum culling).