bug: NullReferenceException

Help!

I encountered two bugs related to NullReferenceException and the error lines are like this:

(1) cs: 36

public void loadStringTable(string filename)
{
TextAsset ta = (TextAsset)Resources.Load("Text/" + filename, typeof(TextAsset));
if (m_stringTable != null) {
m_stringTable = null;
}
m_stringTable = MiniJSON.Json.Deserialize(ta.text) as Dictionary<string, object>;
Resources.UnloadAsset(ta);

(2) cs: 186

public void fadeOut()
{
objMask.GetComponent<Renderer>().material.color = new Color(0.0f, 0.0f, 0.0f, 1.0f);
objMask.GetComponent<Renderer>().enabled = true;
HOTween.To(objMask.GetComponent<Renderer>().material, 0.5f, new TweenParms().Prop("color", new Color(0.0f, 0.0f, 0.0f, 0.0f)).Ease(EaseType.Linear));
Invoke("onDone_FadeOut", 0.5f);

}
void onDone_FadeOut()
{
objMask.GetComponent<Renderer>().enabled = false;
if(m_nextScene.Substring(0, 4) == "Sce_" && !Dialogue.IsEnd){Dialogue.checkEnd();}


I am not a programmer but had learnt a bit of c#. How do I modify those bugs and why do they happen?
Thank you!!

 

It's really hard to read the code in your post. Please use code tags.

 

http://docs.unity3d.com/Manual/NullReferenceException.html

 

No idea how you want us to know which line is line 36 and 186.
Any chance on telling us on which page IDE opens when you double-click error in Unity Editor console?

In first method possible points of failure are:
- null string - filename

I would also consider to always wrap Resources.Load with try-catch block as it will throw an exception on failure.

Also GetComponent<T>() will return null if not found, so I would recommend to assign for example:

Code (CSharp):

1. public void fadeOut()
2. {
3. //Check for nulls down here:
4. if (objMask == null) return;
5. var renderer = objMask.GetComponent<Renderer>();
6. if (renderer == null) return;
7. //Now renderer will be used only if it's not null.
8. renderer.material.color = new Color(0.0f, 0.0f, 0.0f, 1.0f);
9. renderer.enabled = true;
10. HOTween.To(objMask.GetComponent<Renderer>().material, 0.5f, new TweenParms().Prop("color", new Color(0.0f, 0.0f, 0.0f, 0.0f)).Ease(EaseType.Linear));
11. Invoke("onDone_FadeOut", 0.5f);
12.  
13. }

Generally NullPointerException tells you that variable of reference type has not be assigned or points to object that has been already disposed/destroyed.