Fix multiple controllers: protect against empty inactive cmds

[rethink-rlinsalata]

Protect against reading empty msg cmds in inactive controllers, which was causing segfaults when more than 1 controller was loaded and it tried to read values in the cmd that were not populated (e.g. an empty velocity array).

Also fixes wrong #ifndefine in effort_controller.h, and removes leftover JointGroup Controller files/configs.

[IanTheEngineer]

Actually, each commit is self-contained and separate. No squash required.