Fix virtual camera action selection causing a crash

The Create() and Copy() functions were not correctly implemented and
returned a nullptr

plugins/base/macro-action-virtual-cam.cpp

@@ -67,12 +67,12 @@ bool MacroActionVCam::Load(obs_data_t *obj)
 
 std::shared_ptr<MacroAction> MacroActionVCam::Create(Macro *m)
 {
-	return std::shared_ptr<MacroAction>();
+	return std::make_shared<MacroActionVCam>(m);
 }
 
 std::shared_ptr<MacroAction> MacroActionVCam::Copy() const
 {
-	return std::shared_ptr<MacroAction>();
+	return std::make_shared<MacroActionVCam>(*this);
 }
 
 static inline void populateActionSelection(QComboBox *list)