Fix code smells detected by Sonarqube

[platisd]

Description

Sonarqube has detected some code smells and the report can be found here.
Not all of them need to be fixed (i.e. ignore the ones about the commented-out code).

Definition of Done

• Fix the code smells
• Find ways (if any) to avoid regressions (e.g. through clang-tidy or compiler warnings)