setFrameCompletedCallback is only called once, then it crashes

[hannojg]

Describe the bug

We are trying to render into an AVAssetWriter, for that we need to know when the frame is completed.
We are trying to use swapChain->setFrameCompletedCallback for that purpose.
The frame callback is called once, but after that we get an assertion error:

Assertion failed: (mInvoker && mInvocable), function operator(), file Invocable.h, line 134.

To Reproduce

1. Set a frame completed callback using the metal backend:

auto swapChain = _engine->createSwapChain(nativeWindow, SwapChain::CONFIG_APPLE_CVPIXELBUFFER);
  swapChain->setFrameCompletedCallback(
                                       nullptr, [](SwapChain* UTILS_NONNULL swapChain) {
                                           // note: we pass a completely empty callback, and it still crashes
                                       });

Expected behavior

The callback gets called continuously while rendering.

Screenshots

Logs
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Desktop (please complete the following information):

• OS: iOS
• GPU: Apple GPU
• Backend: Metal

Smartphone (please complete the following information):

• Device: iPhone 13 Pro
• OS: iOS 17.4

Additional context

n/a

[hannojg]

cc @mrousavy