ControlReference: Add missing virtual destructor

ControllerEmu::Control instances have a unique_ptr<ControlReference>
member, which is passed either an InputReference or OutputReference.

Without this virtual destructor, deleting a derived class through a
pointer to the base class is undefined behavior.

Source/Core/InputCommon/ControlReference/ControlReference.h

@@ -24,6 +24,7 @@ class ControlReference
 public:
   static bool InputGateOn();
 
+  virtual ~ControlReference();
   virtual ControlState State(const ControlState state = 0) = 0;
   virtual ciface::Core::Device::Control* Detect(const unsigned int ms,
                                                 ciface::Core::Device* const device) = 0;