Unerklärbarer Nullpointer

package awesome.project1.view.render;


import java.io.IOException;
import java.util.Iterator;
import java.util.LinkedList;


import javax.microedition.khronos.opengles.GL10;


import android.content.res.AssetManager;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.opengl.GLUtils;
import android.util.Log;


public class SpriteList extends LinkedList<Sprite> {


	private AssetManager _mngr = null;
	private int[] _texIndices = null;
	private GL10 _gl = null;
	
	public SpriteList (AssetManager mngr, int[] texIndices, GL10 gl) {
		_mngr = mngr;
		_texIndices = texIndices;
		_gl = gl;
	}
	
	public void add(String path, float x, float y, float width, float height, float[] texCoord) throws IOException {
		String id = loadGlTexture(path);
		if (id != null) {
			Sprite s = new Sprite(x, y, width, height, Integer.getInteger(id), path, texCoord);
			this.add(s);
		}
		else
			Log.e("SPRITE", "No usable Tex Id \""+path+"\"");
	}
	
	private String loadGlTexture(String path) throws IOException {
		
		String check = checkGlTexture(path);
		
		if (check.equals("true")) {
			Bitmap image = BitmapFactory.decodeStream(_mngr.open(path));
			_gl.glGenTextures(1, _texIndices, 0);
			int id = _texIndices[0];
			_gl.glBindTexture(GL10.GL_TEXTURE_2D, id);
			_gl.glTexParameterf(GL10.GL_TEXTURE_2D,
								GL10.GL_TEXTURE_MIN_FILTER,
								GL10.GL_LINEAR);
			_gl.glTexParameterf(GL10.GL_TEXTURE_2D,
						   		GL10.GL_TEXTURE_MAG_FILTER,
						   		GL10.GL_LINEAR);
			_gl.glTexParameterf(GL10.GL_TEXTURE_2D,
						   		GL10.GL_TEXTURE_WRAP_S,
						   		GL10.GL_REPEAT);
			_gl.glTexParameterf(GL10.GL_TEXTURE_2D,
						   		GL10.GL_TEXTURE_WRAP_T,
						   		GL10.GL_REPEAT);
			GLUtils.texImage2D(GL10.GL_TEXTURE_2D,
						   		0, image, 0);
			return Integer.toString(id);
		}
		else
			return check;
	}
	
	private String checkGlTexture (String path) {
		for (Sprite s : this){
			if(s.getTexString().equals(path))
				return Integer.toString(s.getTexId());
			else
				return "true";
		}
		return "true";
	}
}

package awesome.project1.view.render;


public class Sprite {


	private float[] _vertex = null;
	private float[] _texCoord = null;
	private String _name = "";
	private int _texId = 0;
	private String _texFile = "";
	
	public Sprite (float top, float left, float width, float height, int id, String tex, float[] texCoord) {
		float[] _v = {	left,top,0.0f,
							left+width,top,0.0f,
							left,top+height,0.0f,
							left+width,top+height,0.0f};
		_vertex = _v;
		if (texCoord == null) {
			float[] _t = {	0.0f,1.0f,
							1.0f,0.0f,
							0.0f,1.0f,
							1.0f,1.0f};
			_texCoord = _t;
		}
		else
			_texCoord = texCoord;
		
		_texFile = tex;
		_texId = id;
	}
	
	public float[] getVertex () {
		return _vertex;
	}
	
	public String getTexString () {
		return _texFile;
	}
	
	public int getTexId () {
		return _texId;
	}
	
	public float[] getTexCoord() {
		return _texCoord;
	}
	
	public String getName() {
		return _name;
	}
	
	public enum SearchIndices {NAME, TEXID};
	
}