Android 无法启动活动组件信息-beginTransaction.add

正如标题所述，我收到

无法启动活动的错误

我对导致错误的部分进行了注释

android是个新手，所以我不确定我是应该上传我所有的其他代码，还是仅仅是那种把事情搞砸的方法

import android.app.Activity;
import android.app.Fragment;
import android.os.Bundle;
import android.util.Log;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toolbar;

import com.dan190.tasks.R;
import com.dan190.tasks.fragment.TaskEditFragment;

public class TaskEditActivity extends Activity {

public static final String EXTRA_TASKID = "taskId";
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    setContentView(R.layout.activity_task_edit);
    setActionBar((Toolbar) findViewById(R.id.toolbar));

    long id = getIntent().getLongExtra(TaskEditActivity.EXTRA_TASKID, 0L);
    Fragment fragment = TaskEditFragment.newInstance(id);
    String fragment_tag = TaskEditFragment.DEFAULT_FRAGMENT_TAG;

/*This is the part that messes it up
 *It works fine if I delete this following if-block
 */
    if (savedInstanceState == null) {
        getFragmentManager().beginTransaction().add(
                R.id.container,
                fragment, 
                fragment_tag).commit();

    }
}
}

编辑：这是错误消息

07-14 00:07:41.666  13945-13945/com.dan190.tasks E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.dan190.tasks, PID: 13945
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.dan190.tasks/com.dan190.tasks.activity.TaskEditActivity}: java.lang.IllegalArgumentException: Target must not be null.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2712)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2777)
        at android.app.ActivityThread.access$900(ActivityThread.java:179)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1462)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:145)
        at android.app.ActivityThread.main(ActivityThread.java:5972)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)
 Caused by: java.lang.IllegalArgumentException: Target must not be null.
        at com.squareup.picasso.RequestCreator.into(RequestCreator.java:553)
        at com.squareup.picasso.RequestCreator.into(RequestCreator.java:536)
        at com.dan190.tasks.fragment.TaskEditFragment.onCreate(TaskEditFragment.java:56)
        at android.app.Fragment.performCreate(Fragment.java:2075)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:868)
        at android.app.FragmentManagerImpl.moveToState(FragmentManager.java:1082)
        at android.app.BackStackRecord.run(BackStackRecord.java:833)
        at android.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1467)
        at android.app.Activity.performStart(Activity.java:6328)
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2675)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2777)
at android.app.ActivityThread.access$900(ActivityThread.java:179)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1462)
at android.os.Handler.dispatchMessage(Handler.java:102)    
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:5972)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1399)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1194)

发布错误也请发布完整的堆栈跟踪，以了解它是如何出错的更新：发布错误！