Unity 5.1.1 is skipping code lines

I have the following code:

 private void scan(GameObject puppet)
     {
         setRunningAway(false);
         _nearbyUnits = puppet.GetComponent<AIPlayerController>().CurrentRegion.UnitsInRegion();
         RaycastHit righthit, lefthit, tophit, bottomhit;
         int _adjacentRegIdx = 0;
         //We'll use an incomplete if-then-else if-else clause to
         //avoid the overhead of having to perform 4 raycasts in a single frame
         //for every AI player.
         if (Physics.Raycast(puppet.transform.position, puppet.transform.forward, out tophit))
         {
             if (tophit.collider.tag == Tags.Region)
             {
                 //We have an available target for our movement to the top of our
                 //current position.
                 _adjacentRegIdx++;
                 movement.Add(tophit.collider.gameObject.transform.position);
                 _adjacentRegions[_adjacentRegIdx - 1] = tophit.collider.gameObject.GetComponent<Region>();
                 
             }
         }
         else if (Physics.Raycast(puppet.transform.position, Vector3.left, out lefthit))
         {
             if (lefthit.collider.tag == Tags.Region)
             {
                 //We have an available target for our movement to the left of our
                 //current position.
                 movement.Add(lefthit.collider.gameObject.transform.position);
                 _adjacentRegions[_adjacentRegIdx] = lefthit.collider.gameObject.GetComponent<Region>();
                 _adjacentRegIdx++;
             }
         }
         else if (Physics.Raycast(puppet.transform.position, Vector3.right, out righthit))
         {
             if (righthit.collider.tag == Tags.Region)
             {
                 //We have an available target for our movement to the right of our
                 //current position.
                 movement.Add(righthit.collider.gameObject.transform.position);
                 _adjacentRegions[_adjacentRegIdx] = righthit.collider.gameObject.GetComponent<Region>();
                 _adjacentRegIdx++;
             }
         }
         else if (Physics.Raycast(puppet.transform.position, puppet.transform.forward * (-1), out bottomhit))
         {
             if (bottomhit.collider.tag == Tags.Region)
             {
                 //We have an available target for our movement to the bottom of our
                 //current position.
                 movement.Add(bottomhit.collider.gameObject.transform.position);
                 _adjacentRegions[_adjacentRegIdx] = bottomhit.collider.gameObject.GetComponent<Region>();
             }
         }
 
         _regionsIdentified = _adjacentRegIdx + 1;
     }

which is used by my AI to get a sense of its current surroundings. For some reason, I kept getting NullReferenceException messages when I hit play on Unity. When I tried debugging with Visual Studio, I realized that in this code segment:

 if (Physics.Raycast(puppet.transform.position, puppet.transform.forward, out tophit))
         {
             if (tophit.collider.tag == Tags.Region)
             {
                 //We have an available target for our movement to the top of our
                 //current position.
                 movement.Add(tophit.collider.gameObject.transform.position);
                 _adjacentRegions[_adjacentRegIdx] = tophit.collider.gameObject.GetComponent<Region>();
                 _adjacentRegIdx++;
 
             }
         }

it skips the first two lines of code within the two if clauses and goes directly to the last ( _adjacentRegIdx++;), causing the exception later on, when I use the array _adjacentRegions. From what I know of programming so far this shouldn't be happening. Any ideas why it is?

P.S.:The code for class Region works, I have already tested it thoroughly; but here it is anyway.

P.S.1: I use Visual Studio 2015 Enterprise Edition.

 public class Region: MonoBehaviour
 {
     //Definition: A region is a polygonal area with a center, which
     // provides data about the players traversing it.
     public RegionBoundary[] boundaries;
 
     /// <summary>
     /// The center of the region, which is defined as the position
     /// of the parent game object.
     /// </summary>
     public Vector3 RegionCenter
     {
         get
         {
             return transform.position;
         }
     }
 
     private List<GameObject> members;
 
     void Awake()
     {
         members = new List<GameObject>();
     }
 
     /// <summary>
     /// Updates the region with any entries or exits (of any AI or of the player).
     /// </summary>
     /// <param name="unit">One of the AI or the player.</param>
     public void UpdateRegion(GameObject unit)
     {
         if(!members.Contains(unit))
         {
             if (unit.tag == Tags.AIPlayerController)
                 unit.GetComponent<AIPlayerController> ().CurrentRegion = this;
             else
                 unit.GetComponent<PlayerController> ().CurrentRegion = this;
             
             members.Add(unit);
         }
         else
         {
             if (unit.tag == Tags.AIPlayerController)
                 unit.GetComponent<AIPlayerController> ().CurrentRegion = null;
             else
                 unit.GetComponent<PlayerController> ().CurrentRegion = null;
             
             members.Remove(unit);
         }
     }
 
     /// <summary>
     /// Returns all units in this region
     /// </summary>
     public List<GameObject> UnitsInRegion()
     {
         return members;
     }
 }