Error in android layout according to layout arrange dependencies

When I change the arrange of layouts, and change dependency accordingly, i get an exception.

I have the following layout (causes the error):

Layout XML

    <LinearLayout
      android:id="@+id/followerssLayout"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_below="@+id/tagsLayout">
      <ImageView
          android:id="@+id/imgFollowers"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:background="@android:color/transparent"
          android:scaleType="fitXY"
          android:src="@drawable/ic_users"
          android:contentDescription="@drawable/ic_users" />
      <TextView
          android:id="@+id/lblSelectedFollowers"
          android:layout_width="0dp"
          android:layout_height="wrap_content"
          style="@style/LabelData"
          android:paddingLeft="5dp"
          android:paddingRight="5dp"
          android:layout_weight=".75"
          android:hint="@+string/select_followers" />
      <ImageButton
          android:id="@+id/imgbAddUsers"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:background="@android:color/transparent"
          android:scaleType="fitXY"
          android:src="@drawable/ic_add_user"
          android:contentDescription="@drawable/ic_add_user"
          android:visibility="gone" />
  </LinearLayout>
  <LinearLayout
      android:id="@+id/buttonsLayout"
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      android:layout_below="@+id/followerssLayout"
      android:paddingBottom="15sp">
      <Button
          android:id="@+id/btnDeleteTask"
          style="@style/Widget.Button"
          android:layout_width="0dp"
          android:layout_height="wrap_content"
          android:layout_marginTop="20dp"
          android:text="@string/delete"
          android:layout_weight=".5"
          android:layout_marginLeft="5sp"
          android:layout_marginStart="5sp"
          android:layout_marginRight="5sp"
          android:layout_marginEnd="5sp" />
      <Button
          android:id="@+id/btnSaveTask"
          style="@style/Widget.Button"
          android:layout_width="0dp" 
          android:layout_height="wrap_content"
          android:layout_marginTop="20dp"
          android:text="@string/save"
          android:layout_weight=".5"
          android:layout_marginLeft="5sp"
          android:layout_marginStart="5sp"
          android:layout_marginRight="5sp"
          android:layout_marginEnd="5sp" />
  </LinearLayout>
  <LinearLayout
      android:id="@+id/subTasksLayout"
      android:layout_width="wrap_content"
      android:layout_height="wrap_content"
      android:layout_below="@+id/buttonsLayout"
      android:paddingBottom="15sp">
      <ImageView
          android:id="@+id/imgSubTasks"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:background="@android:color/transparent"
          android:scaleType="fitXY"
          android:src="@drawable/ic_sub_tasks"
          android:contentDescription="@drawable/ic_sub_tasks" />
      <ListView
          android:id="@+id/lstSubTasks"
          android:layout_width="0dp"
          android:layout_height="wrap_content"
          android:layout_weight=".55">
      </ListView>
      <TextView
          android:id="@+id/lblEmpty"
          android:hint="@string/add_subtask"
          android:layout_width="wrap_content"
          android:layout_height="wrap_content"
          android:gravity="center_horizontal"
          android:layout_gravity="center_vertical"
          android:visibility="gone"
          style="@style/LabelData">
      </TextView>
  </LinearLayout>

This causes the following exception:

Exception

05-18 18:29:35.897: E/AndroidRuntime(1508): FATAL EXCEPTION: main
05-18 18:29:35.897: E/AndroidRuntime(1508): java.lang.ClassCastException:
    android.widget.Button cannot be cast to android.widget.ListView
05-18 18:29:35.897: E/AndroidRuntime(1508):     at com.horizons.engiz.ui.FragManageTask.onCreateView(FragManageTask.java:142)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.support.v4.app.Fragment.performCreateView(Fragment.java:1504)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:942)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.support.v4.app.FragmentManagerImpl.moveToState(FragmentManager.java:1121)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.support.v4.app.BackStackRecord.run(BackStackRecord.java:682)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.support.v4.app.FragmentManagerImpl.execPendingActions(FragmentManager.java:1484)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.support.v4.app.FragmentManagerImpl$1.run(FragmentManager.java:450)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.os.Handler.handleCallback(Handler.java:615)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.os.Handler.dispatchMessage(Handler.java:92)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.os.Looper.loop(Looper.java:137)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at android.app.ActivityThread.main(ActivityThread.java:4745)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at java.lang.reflect.Method.invokeNative(Native Method)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at java.lang.reflect.Method.invoke(Method.java:511)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
05-18 18:29:35.897: E/AndroidRuntime(1508):     at dalvik.system.NativeStart.main(Native Method)

Important info: when i put buttons Layout below sub Tasks Layout and change layout_below accordingly , it works fine

any help will be most appreciated