Drawable not showing up

I have a fairly simple xml file that has an image button in it. The image shows up fine on the Graphical Layout xml designer, shows up fine when I run a development build, but as soon as I create the signed apk file and run it, the image no longer shows up. It's just an empty button. I can't think of a reason why, any ideas? The xml file looks like this:

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/navigation_root"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/navigation_text"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="5dp"
        android:text="TextView"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <SeekBar
        android:id="@+id/navigation_seekbar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="center_vertical"
        android:layout_weight="1"
        android:padding="5dp" />

    <LinearLayout
        android:id="@+id/linearLayout1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:padding="5dp" >

        <ImageButton
            android:id="@+id/part_select_button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:src="@drawable/chapter_select" />

        <Button
            android:id="@+id/navigation_ok_button"
            android:layout_width="75dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="@string/ok" />

        <Button
            android:id="@+id/navigation_cancel_button"
            android:layout_width="75dp"
            android:layout_height="match_parent"
            android:layout_weight="1"
            android:text="@string/cancel" />
    </LinearLayout>
</LinearLayout>

The image @drawable/chapter_select is a fairly small (41*41) png file that is in the res/drawable folder.

Seems like this is a bug with android, where sometimes the first image in the drawable folder doesn't show up. Added a dummy image called aaaa.png to the drawable folder and problem was solved. Found the answer here: ImageButton does not display a particular drawable