[C# Code] Why am I getting this error???

I have a function to update a placeholder UI made up of 4 3d text objects (sorry for the long names):

 private void updateUnitStatsUIWindow(ArmyUnit script)
 {
 costs.GetComponent<TextMesh>().text = "Costs (M - A): " + script.getMoveCost() + " - " + script.getAttackCost();
 atkInfo.GetComponent<TextMesh>().text = "Range - Dmg: " + script.getAttackRange() + " - " + script.getAttackDamage();
 health.GetComponent<TextMesh>().text = "Health: " + script.getCurrHealth() + " / " + script.getMaxHealth();
 level.GetComponent<TextMesh> ().text = "Level (Exp): " + script.getLevel() + " (" + script.getExperience() + " / " + script.getExpNeededForNextLevel() + ")";
 }

Which results in something like this (top left corner): http://i.imgur.com/yHI85Gb.jpg

I call the function defined above when a unit is selected and when making the unit (because it is selected when it's first made). ArmyUnit is a script attached to the unit that has all the get functions.

1) here is the code for when the unit is made:

 //selects the newly created unit and sets the stats at the top left to its stats
 public void onNewUnitCreation(GameObject newUnit)
 {
     currentlySelectedUnit = newUnit;

     showUnitSelectionMarker(newUnit);
     updateUnitStatsUIWindow(currentlySelectedUnit.GetComponent<ArmyUnit>());
     statsWindowUIPLACEHOLDER.SetActive(true);
 }

2) here is the code for when the unit is SELECTED:

 if(Input.GetMouseButtonDown(0) && Physics.Raycast(ray, out hit, 500f, gameControl.getUnitLayer()))
     {
         currentlySelectedUnit = hit.collider.gameObject;
         showUnitSelectionMarker(hit.collider.gameObject);
         updateUnitStatsUIWindow(currentlySelectedUnit.GetComponent<ArmyUnit>());
         statsWindowUIPLACEHOLDER.SetActive(true);
     }

PROBLEM: Whenever the unit is SELECTED I get an error. Whenever the unit is CREATED, I do not. WHY?

THE ERROR:

 NullReferenceException: Object reference not set to an instance of an object
 SingleUnitControl.updateUnitStatsUIWindow (.ArmyUnit script) (at Assets/Scripts/SingleUnitControl.cs:99)
 SingleUnitControl.Update () (at Assets/Scripts/SingleUnitControl.cs:43)