Error NullReferenceException

Question

This is the exception I'm getting:

A first chance exception of type 'System.NullReferenceException' occurred in Bile.exe

Additional information: Object reference not set to an instance of an object.

Code:

Cerc ceva = GenerateNewParticle();
cercuri.Add(ceva);

The error is in second line, and i don't know why, because my function shouldn't return null

public Cerc GenerateNewParticle()
    {

        Vector2 position = Location;
        Random random = new Random();
        Color color = new Color(
                    (float)random.NextDouble(),
                    (float)random.NextDouble(),
                    (float)random.NextDouble());

        return new Cerc(Texture, position, color);
    }

This is from Cerc class

public class Cerc
{
    public Texture2D Texture;
    public Color Color;
    float x = 0, y = 0;
    float varx = 2, vary = 2;
    public Cerc(Texture2D texture,Vector2 location,Color color)
    {
        x = location.X + 50;
        y = location.Y + 50;
        Texture = texture;
        Color = color;
    }