Android : Resizing AlertDialog To Fit Image

I have the following AlertDialog with an image inside it:As you can see there is a small gap just above and just below the image. I'd like to remove that gap.My layout xml looks like:

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

<ImageView android:id="@+id/thumb"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>