run_algo fails when no observation is available for the first analysis
KeyError: ER when trying to get the misfits after the first analysis if no observations is available.
current_misfits is initiated to an empty dict. If no observation is available, the misfits dict is not populated and therefore has no keys.
current_misfits with the needed keys thanks to a method of
analyser, overridden to add
PCA_U if needed (similar to what is already done for