RuntimeError running LoopBpmEstimator on very short inputs

[dbogdanov]

LoopBpmEstimator is not supposed to work on very short inputs. Should it still accept such inputs and provide 0 BPM value?

Currently, it results in this exception with a misleading text:

from essentia.standard import LoopBpmEstimator
LoopBpmEstimator(confidenceThreshold=0.95)([0] * 1000)

results in

RuntimeError: In LoopBpmEstimator.compute: Descriptor name 'lags' of type std::vector<Real> not found

[ffont]

Makes sense to return 0 BPM value if algorithm is not supposed to work with that signal.