If various functions on l_Control_Info were called while Player was nullptr, FSO would CTD due to a null pointer dereference. This commit adds nullptr checks to avoid the problem.
When using a string to define the appropriate control in the useButtonControl() function (in l_Control_Info), the command definition was being divided by 32 when the appropriate mathematical operator was modulo; as a result, the only controls that could actually wind up being referenced are these four: TARGET_NEXT, MAX_THROTTLE, END_MISSION, and MULTI_MESSAGE_HOSTILE. By using the modulo operator, the string lookup now appropriately references the relevant button.
This maintains the type information which can be used for enforce
const-correctness and also for implementing more advanced ways of
handling the type information.
MageKing17