NullPointerException when using RelativeLayout as custom InfoWindow

I'm trying to use a RelativeLayout as custom InfoWindow for my markers, but a I get a NullPointerException every time showInfoWindow is called (via tapping on a Marker or programmatically). I'm using Google Maps Android API v2.

Exception:

FATAL EXCEPTION: main
java.lang.NullPointerException
    at android.widget.RelativeLayout.onMeasure(RelativeLayout.java:465)
    at android.view.View.measure(View.java:15172)
    at maps.a.y.i(Unknown Source)
    at maps.a.y.a(Unknown Source)
    at maps.a.w.a(Unknown Source)
    at maps.a.bd.a(Unknown Source)
    at maps.y.bw.b(Unknown Source)
    at maps.y.bw.a(Unknown Source)
    at maps.a.dh.a(Unknown Source)
    at maps.a.n.c(Unknown Source)
    at maps.a.dw.a(Unknown Source)
    at maps.a.bd.c(Unknown Source)
    at maps.a.dq.onSingleTapConfirmed(Unknown Source)
    at maps.e.v.onSingleTapConfirmed(Unknown Source)
    at maps.e.j.handleMessage(Unknown Source)
    ...

My code:

*custom_infowindow.xml*

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:padding="10dip" >

    <ImageView
        android:id="@+id/icon"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:paddingLeft="10dip"
        android:paddingRight="10dip"
        android:paddingTop="5dip"
        android:src="@drawable/icon" />

    <TextView
        android:id="@+id/title"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_toLeftOf="@id/icon"
        android:ellipsize="end"
        androi