Null Reference Exception only when using debugger

My code is throwing a NullReferenceException but only when attempting to use the MonoDeveloper debugger. I have no idea why. (Also sometimes it doesn't throw an exception...it seems totally random).

Here is the code. Exception is thrown for line 20.

 using UnityEngine;
 using System.Collections;
 using System.Collections.Generic;
 
 public class LineDrawer : MonoBehaviour {
 
     public Material lineMat;
     private List<Vector3> points, vPoints;
     Body[] lineDrawerSubjects;
 
 //    Material lineMat2 = new Material ("Shader \"Lines/Colored Blended\" {" +
 //                        "Subshader { Pass { " +
 //                        "Blend SrcAlpha OneMinusSrcAlpha " +
 //                        "ZWrite Off Cull Off Fog {Mode Off} " +
 //                        "Bind Channels { " +
 //                        "Bind \"vertex\", vertex Bind \"color\", color}" +
 //                        "} } }");
 
     public void DrawConnectingLines(){
         foreach (Body lineDrawerSubject in lineDrawerSubjects) {
             points = lineDrawerSubject.orbitPositions;
             vPoints = lineDrawerSubject.orbitVelocities;
             if (points.Count > 1) {
                 float len = points.Count;
                 //lineMat.SetColor ("Color", Color.red);
                 lineMat.SetPass (0);
                 Color startColor;
                 if (lineDrawerSubject is Ship) {
                     startColor = new Color (0, 1, 1, 1);
                 } else if (lineDrawerSubject is Bullet) {
                     startColor = new Color (1, 1, 1, 1);
                 } else {
                     startColor = new Color (1, 1, 1, 1);
                 }
                 Color endColor = new Color (0, 0, 0, 0);
                 GL.Begin (GL.LINES);
                 for (int i = 0; i < points.Count - 1; i++) {    
                     GL.Color(Color.Lerp (startColor, endColor, i/len));
                     GL.Vertex3 (points [i].x, points [i].y, points [i].z);
                     GL.Vertex3 (points [i + 1].x, points [i + 1].y, points [i + 1].z);
                 }
                 GL.End ();
                 GL.Begin (GL.LINES);
                 GL.Color (Color.yellow);
                 GL.Vertex3 (points [0].x, points [0].y, points [0].z);
                 GL.Vertex3 (vPoints [0].x + points[0].x,vPoints [0].y + points[0].y, vPoints [0].z + points[0].z);
                 GL.End ();
             }
         }
     }
 
     void OnDrawGizmos() {
         DrawConnectingLines();
     }
 
     void OnPostRender() {
         DrawConnectingLines();
     }
 
     void UpdateSubjects(){
         lineDrawerSubjects = FindObjectsOfType (typeof(Body)) as Body[];
     }
 
     void Start(){
         points = new List<Vector3>();
         UpdateSubjects ();
         //lineDrawerSubjects = FindObjectsOfType (typeof(Body)) as Body[];
     }
 }