Replacing outerHTML more than once - Android Webview

Question

I am trying to make some modifications to an XHTML page using the outerHTML element, accessed via a Javascript function. The Javascript function that does this is called from an Android WebView like so:
1. Push a button, Javascript function is called which accesses outerHTML element, stores and, just for the sake of it, assigns it to another variable and replaces it like so: document.getElementById("bodyTag").outerHTML = newHTML

All of this works fine when the button is pressed the first time. Pressing it the second time results in the following LogCat error:

09-14 13:24:21.432: V/com.sriram.outerhtml.OuterHTML$2@4052e0f8(10931): Clicked click!
09-14 13:24:21.432: V/com.sriram.outerhtml.OuterHTML@40520da8(10931): Replacing outerHTML
09-14 13:24:21.452: D/com.sriram.outerhtml.OuterHTML$1@4052dcf8(10931): jswebview: Function to replace outerHTML.. with itself of level = LOG at line: 410
09-14 13:24:21.452: D/com.sriram.outerhtml.OuterHTML$1@4052dcf8(10931): jswebview: Uncaught TypeError: Cannot read property 'outerHTML' of null of level = ERROR at line: 411  

My questions:
1. The error indicates that the element with that tag is not available in the document. But that is not the case since it works the first time around. Where is the error?
2. How do I get this right?

The code:
OuterHTML.java:

/*
 * Each time the button is clicked, a javascript function is invoked.
 * Javascript function: Takes outerHTML, assigns it to new variable and replaces it.
 */

package com.sriram.outerhtml;

import java.io.File;

import android.app.Activity;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.webkit.ConsoleMessage;
import android.webkit.WebChromeClient;
import android.webkit.WebView;
import android.widget.Button;

public class OuterHTML extends Activity {

    private WebView wv;
    private Button click;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_outer_html);

        wv = (WebView) findViewById(R.id.webview);
        wv.getSettings().setJavaScriptEnabled(true);

        String path = Environment.getExternalStorageDirectory().getAbsolutePath() + "/JsWebView/";
        String path_file = "file:///" + path + "mypage_copy.xhtml";

        wv.loadUrl(path_file);

         wv.setWebChromeClient(new WebChromeClient() {

            @Override
            public boolean onConsoleMessage(ConsoleMessage cm) {
                /* 
                 * 1.Override console message to display messages from the javascript function.
                 */
                if(cm.messageLevel().equals("ERROR")) {
                    Log.d(this.toString(), "jswebview: " + cm.message() + " of level = " + cm.messageLevel() + " at line: " + cm.lineNumber());
                } else {
                    Log.d(this.toString(), "jswebview: " + cm.message() + " of level = " + cm.messageLevel() + " at line: " + cm.lineNumber());
                }
                return true;
            }
         });

        click = (Button) findViewById(R.id.click);
        click.setOnClickListener(new View.OnClickListener() {

            @Override
            public void onClick(View v) {
                Log.v(this.toString(), "Clicked click!");
                replaceOuterHTML();
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.outer_html, menu);
        return true;
    }

    public void replaceOuterHTML() {
        Log.v(this.toString(), "Replacing outerHTML");
        wv.loadUrl("javascript:replaceOuterHTML()");
    }
}

Layout:

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".OuterHTML" >

    <Button
        android:id="@+id/click"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_alignParentBottom="true"
        android:text="Click" />

    <WebView
        android:id="@+id/webview"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_above="@id/click"
        android:text="@string/hello_world" />

</RelativeLayout>

The XHTML page:

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"
 "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en" lang="en">
<head>
<meta content="application/xml+xhtml;charset=UTF-8" />
<script src="highlightWordInSentence.js" type="text/javascript"></script>
<script src="jquery-2.0.2.min.js"> </script>
<title>Building your resume</title>
</head>
<body xmlns="http://www.w3.org/1999/xhtml" id="highlightbegin">
<h1>Building your resume</h1>
</body>  
</html>  

And the Javascript function:

function replaceOuterHTML() {

    console.info("Function to replace outerHTML.. with itself");
    var oldHTML = document.getElementById("highlightbegin").outerHTML;
    if(!oldHTML) {
        console.error("oldHTML is null.");
    } else {
        console.info("replacing oldHTML");
        var newHTML = oldHTML;
        document.getElementById("highlightbegin").outerHTML = newHTML;
    }
}