Remove warnings/bugs detected by sonarqube
See the web page at https://hpclib-sed.bordeaux.inria.fr/sonarqube/component_issues?id=scalfmm#resolved=false|types=BUG like Member variable XX is not initialized in the constructor
See the web page at https://hpclib-sed.bordeaux.inria.fr/sonarqube/component_issues?id=scalfmm#resolved=false|types=BUG like Member variable XX is not initialized in the constructor