for-loop + array equals "NullReferenceException: Object reference not set to an instance of an object" ? (SOLVED)

[yodale]

Hey Guys I have a huge problem. first of sorry for the german names of my variables.

whenever I run this:

using UnityEngine;
using System.Collections;

public class palme : MonoBehaviour {

    public float[,] m_bomben;
    public bool m_wurfBereit = true;

    public int m_bombenMenge = 1;

    public float m_laengeBlock = 1.0f;

    public int m_laengeMapInBloecken = 11;
    public int m_breiteMapInBloecken = 11;

    System.Random rng = new System.Random();

    public float m_zufallszahlen(int i)
    {
        return (rng.Next(-1 * (i / 2), (i / 2))) * m_laengeBlock;
    }

	void Start () 
    {
      float[,] m_bomben = new float[m_bombenMenge, 2];
    }

	void Update () 
    {
        if (m_wurfBereit)
        {
                for (int i = 0; i < m_bombenMenge; i++)
                {
                    Debug.Log("i ist " + i);
                    m_bomben[i, 0] = m_zufallszahlen(m_laengeMapInBloecken);
                    m_bomben[i, 1] = m_zufallszahlen(m_breiteMapInBloecken);
                    Debug.Log(m_bomben[i,1]);
                }
            }        
            m_wurfBereit = false;
        }
    }

Unity gives me the Error
“NullReferenceException: Object reference not set to an instance of an object”

But I just don’t know why !?
It some how seems to be the Array that messes up.

PS.: I’m pretty new to C# and Unity so there might just be weird coding none would write

[yodale]

I found the fault !

line 25.: float[,] m_bomben = new float[m_bombenMenge, 2];

I’m not setting my m_bomben array, but creating a complete new one in the Start()