title: Data binding: set property if it isn't null
body: <p>Cannot understand... How to set some property of view only if variable field isn't null?
  <br>For example</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="utf-8"?&gt;
  &lt;layout xmlns:android="http://schemas.android.com/apk/res/android"&gt;
  
      &lt;data&gt;
          &lt;variable
              name="item"
              type="com.test.app.Item" /&gt;
      &lt;/data&gt;
  
      &lt;RelativeLayout
          android:layout_width="match_parent"
          android:layout_height="60dp"
          android:orientation="horizontal"&gt;
  
          &lt;ImageView
              android:id="@+id/icon"
              android:layout_width="wrap_content"
              android:layout_height="wrap_content"
              android:layout_alignParentLeft="true"
              android:layout_alignParentStart="true"
              android:layout_centerVertical="true"
              android:layout_margin="16dp"
              android:src="@{item.getDrawable()}"/&gt;
  
          &lt;LinearLayout
              android:layout_width="match_parent"
              android:layout_height="wrap_content"
              android:layout_centerVertical="true"
              android:layout_marginEnd="16dp"
              android:layout_marginLeft="72dp"
              android:layout_marginRight="16dp"
              android:layout_marginStart="72dp"
              android:layout_toLeftOf="@id/action"
              android:layout_toStartOf="@id/action"
              android:orientation="vertical"&gt;
  
              &lt;TextView
                  android:id="@+id/text1"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:singleLine="true"
                  android:textColor="@color/black_87"
                  android:textSize="16sp"
                  android:text="@{item.getTitle()}"/&gt;
  
              &lt;TextView
                  android:id="@+id/text2"
                  android:layout_width="match_parent"
                  android:layout_height="wrap_content"
                  android:autoLink="web|email"
                  android:linksClickable="false"
                  android:singleLine="true"
                  android:textColor="@color/black_54"
                  android:textSize="14sp"
                  android:text="@{item.getSubtitle()}"/&gt;
  
  
          &lt;/LinearLayout&gt;
  
      &lt;/RelativeLayout&gt;
  &lt;/layout&gt;
  </code></pre>
  
  <p>Some field of Item can be null and I won't call methods of layout views unnecessarily. And I won't get <code>NullPointerException</code>. How can I set property only if it isn't null?
  <br>P.S. Sorry for English.</p>