MissingReferenceException

using System;
using Holoville.HOTween.Path;
using UnityEditor;
using UnityEngine;

[CustomEditor(typeof (SomeMonobehavior))]
public class SomeMonobehaviorEditor : Editor
{
    public override void OnInspectorGUI()
    {
        DrawDefaultInspector();
        if (GUILayout.Button("remove and add component"))
        {
            var gameObject = ((SomeMonobehavior) target).gameObject;
            try
            {
                // Illustrating with BoxCollider as example
                var old = gameObject.GetComponent<BoxCollider>();
                if (old != null)
                {
                    DestroyImmediate(old);
                }
            }
            catch (NullReferenceException)
            {
                // this occurs properly when the object does not exist (though the != null is catching it now)
            }
            catch (MissingReferenceException)
            {
                // the code never enters here, even though the exception is of this type.
            }

            // add it again
            var path = gameObject.AddComponent<BoxCollider>();
        }
    }
}