Add an assertion to the discrete_space function and a death test#875

tpadioleau merged 3 commits intomainCExA-project/ddc:mainfrom

874-raise-error-when-using-ddcdiscrete_space-if-not-initialisedCExA-project/ddc:874-raise-error-when-using-ddcdiscrete_space-if-not-initialisedCopy head branch name to clipboard