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.cpp

@@ -52,6 +52,8 @@ ControlReference::ControlReference() : range(1), m_parsed_expression(nullptr)
 {
 }
 
+ControlReference::~ControlReference() = default;
+
 InputReference::InputReference() : ControlReference()
 {
 }