IndexError for AutoQKeras with hyperband mode

I get the following stack trace when calling `get_best_model()` on the AutoQKeras object using hyperband mode:
```
Traceback (most recent call last):
File "exp_nns.py", line 533, in
auto_qkeras_model = t.auto_mnist_cnn(auto_qkeras=True, mode="hyperband", tune_filter="layer", activation_bits=8)
File "exp_nns.py", line 387, in auto_mnist_cnn
aqnn = autoqk.get_best_model()
File "~/.pyenv/versions/hls4ml_venv/lib/python3.8/site-packages/qkeras/autoqkeras/autoqkeras_internal.py", line 976, in get_best_model
params = self.tuner.get_best_hyperparameters()[0]
IndexError: list index out of range
```

It does not run into an error if I use `random` or `bayesian` mode. Does anyone know what could be causing this IndexError?