Filtering up, in case that itself is already enough to find it:
NullReferenceException: Object reference not set to an instance of an object
at NASA_CountDown.ModuleNASACountdown.CraftName (Vessel v) [0x0003d] in <22f3824a41ad4b04b860228c32c04d8c>:0
at NASA_CountDown.Config.ConfigInfo.InitNewConfig () [0x0001f] in <22f3824a41ad4b04b860228c32c04d8c>:0
at NASA_CountDown.CountDownMain.ToggleOn () [0x00024] in <22f3824a41ad4b04b860228c32c04d8c>:0
at ToolbarControl_NS.ToolbarControl.SetButtonActive () [0x00012] in <6186cefd4f6f47a9b00314aa25a7784b>:0
at ToolbarControl_NS.ToolbarControl.doOnTrue () [0x00011] in <6186cefd4f6f47a9b00314aa25a7784b>:0
at (wrapper delegate-invoke) <Module>.invoke_void()
at KSP.UI.Screens.ApplicationLauncherButton.OnTrue (UnityEngine.EventSystems.PointerEventData data, KSP.UI.UIRadioButton+CallType callType) [0x00000] in <39c0323fb6b449a4aaf3465c00ed3c8d>:0
at UnityEngine.Events.InvokableCall`2[T1,T2].Invoke (T1 args0, T2 args1) [0x00010] in <12e76cd50cc64cf19e759e981cb725af>:0
at UnityEngine.Events.UnityEvent`2[T0,T1].Invoke (T0 arg0, T1 arg1) [0x00025] in <12e76cd50cc64cf19e759e981cb725af>:0
at KSP.UI.UIRadioButton.SetState (KSP.UI.UIRadioButton+State state, KSP.UI.UIRadioButton+CallType callType, UnityEngine.EventSystems.PointerEventData data, System.Boolean popButtonsInGroup) [0x00079] in <39c0323fb6b449a4aaf3465c00ed3c8d>:0
at KSP.UI.UIRadioButton.ToggleState (KSP.UI.UIRadioButton+CallType callType, UnityEngine.EventSystems.PointerEventData data) [0x00026] in <39c0323fb6b449a4aaf3465c00ed3c8d>:0
at KSP.UI.UIRadioButton.UnityEngine.EventSystems.IPointerClickHandler.OnPointerClick (UnityEngine.EventSystems.PointerEventData eventData) [0x0011e] in <39c0323fb6b449a4aaf3465c00ed3c8d>:0
at UnityEngine.EventSystems.ExecuteEvents.Execute (UnityEngine.EventSystems.IPointerClickHandler handler, UnityEngine.EventSystems.BaseEventData eventData) [0x00007] in <5336a8686ff14f17888ce9a9f44f29bc>:0
at UnityEngine.EventSystems.ExecuteEvents.Execute[T] (UnityEngine.GameObject target, UnityEngine.EventSystems.BaseEventData eventData, UnityEngine.EventSystems.ExecuteEvents+EventFunction`1[T1] functor) [0x00063] in <5336a8686ff14f17888ce9a9f44f29bc>:0
UnityEngine.DebugLogHandler:Internal_LogException(Exception, Object)
UnityEngine.DebugLogHandler:LogException(Exception, Object)
ModuleManager.UnityLogHandle.InterceptLogHandler:LogException(Exception, Object)
UnityEngine.Logger:LogException(Exception, Object)
UnityEngine.Debug:LogException(Exception)
UnityEngine.EventSystems.ExecuteEvents:Execute(GameObject, BaseEventData, EventFunction`1)
UnityEngine.EventSystems.StandaloneInputModule:ReleaseMouse(PointerEventData, GameObject)
UnityEngine.EventSystems.StandaloneInputModule:ProcessMousePress(MouseButtonEventData)
UnityEngine.EventSystems.StandaloneInputModule:ProcessMouseEvent(Int32)
UnityEngine.EventSystems.StandaloneInputModule:ProcessMouseEvent()
UnityEngine.EventSystems.StandaloneInputModule:Process()
UnityEngine.EventSystems.EventSystem:Update()
(Filename: <22f3824a41ad4b04b860228c32c04d8c> Line: 0)
Full log here.