Why my app crashed when im Calling Image picker from a fragment?

Question

I have a fragment that calls the loadImagpicker from the activity but when Tap on the Image view it crashes. I ve been doing everything on the activity and I created a callback so where I can retrieve the Image Uri if its good here is my code.

imageHolder.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                BluEnergyTag b =  new BluEnergyTag(new BluEnergyTag.ImagePickerCallback() {
                    @Override
                    public void onImageSelected(Uri imageUri) {
                        imageHolder.setImageURI(imageUri);
                    }
                });
                b.loadImagePicker();
            }
        });

and this is how I made my loadImagePicker in activity

public ImagePickerCallback mCallback;
    private static final int GALLERY_REQUEST = 1;

    public interface ImagePickerCallback{
        void onImageSelected(Uri imageUri);
    }
    public BluEnergyTag(){

    }

public void loadImagePicker(){
        Intent i = new Intent(Intent.ACTION_PICK,android.provider.MediaStore.Images.Media.EXTERNAL_CONTENT_URI);
        startActivityForResult(i,1);
    }
    @Override
    protected void onActivityResult(int requestCode, int resultCode, Intent data) {
        super.onActivityResult(requestCode, resultCode, data);
        if (requestCode == GALLERY_REQUEST && resultCode == RESULT_OK){
            mCallback.onImageSelected(data.getData());
        }
    }

and this is my Log

06-07 12:52:29.404 23839-23839/bluenergyfuel.bluenergytag E/AndroidRuntime: FATAL EXCEPTION: main
                                                                            Process: bluenergyfuel.bluenergytag, PID: 23839
                                                                            java.lang.NullPointerException: Attempt to invoke virtual method 'android.app.ActivityThread$ApplicationThread android.app.ActivityThread.getApplicationThread()' on a null object reference
                                                                                at android.app.Activity.startActivityForResult(Activity.java:4226)
                                                                                at android.support.v4.app.BaseFragmentActivityJB.startActivityForResult(BaseFragmentActivityJB.java:50)
                                                                                at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:79)
                                                                                at android.app.Activity.startActivityForResult(Activity.java:4183)
                                                                                at android.support.v4.app.FragmentActivity.startActivityForResult(FragmentActivity.java:859)
                                                                                at bluenergyfuel.bluenergytag.BluEnergyTag.loadImagePicker(BluEnergyTag.java:202)
                                                                                at bluenergyfuel.bluenergytag.drawer.PartnerStorePost$1.onClick(PartnerStorePost.java:65)
                                                                                at android.view.View.performClick(View.java:5637)
                                                                                at android.view.View$PerformClick.run(View.java:22429)
                                                                                at android.os.Handler.handleCallback(Handler.java:751)
                                                                                at android.os.Handler.dispatchMessage(Handler.java:95)
                                                                                at android.os.Looper.loop(Looper.java:154)
                                                                                at android.app.ActivityThread.main(ActivityThread.java:6176)
                                                                                at java.lang.reflect.Method.invoke(Native Method)
                                                                                at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:888)
                                                                                at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:778)