Obtengo una NPE cuando intento iniciar la aplicación. No sé qué lo causa. La aplicación debe mostrar un mapa en un sitio web. Luego, el usuario puede escribir fácilmente su ubicación en el texto de edición y enviarlo a la página web. Aquí está mi código:

package com.timbremer.iimv;

import android.content.Context;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.app.ActionBar;
import android.support.v4.app.Fragment;
import android.os.Bundle;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.ViewGroup;
import android.os.Build;
import android.view.inputmethod.InputMethodManager;
import android.webkit.CookieManager;
import android.webkit.WebView;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.EditText;

public class MainActivity extends ActionBarActivity {

private WebView wv;
private EditText etlocation;
private Button btclose;
private Button btgo;
private boolean send;

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

    send = false;


    etlocation = (EditText) findViewById(R.id.etlocation);
    btgo.setOnClickListener(new View.OnClickListener() {

        private String location;


        @Override
        public void onClick(View v) {
             location = etlocation.getText().toString();

     WebView wv = (WebView) findViewById(R.id.wv);
            wv.getSettings().setBuiltInZoomControls(true);
            CookieManager.getInstance().setAcceptCookie(true);
            wv.getSettings().setJavaScriptEnabled(true);
            wv.getSettings().setLoadWithOverviewMode(true);
            wv.getSettings().setUseWideViewPort(true);
            wv.loadUrl("http://www.ingress.com/intel");
            wv.setWebViewClient(new WebViewClient() {

                @Override
                public boolean shouldOverrideUrlLoading(WebView view, String url) {
                    view.loadUrl(url);
                    return true;
                }
                @Override
                public void onPageFinished(WebView view, String url) {
                    if(!send) {
                        view.loadUrl("javascript:{" +
                                "document.getElementById('adress').value='" + location + "';" +
                                "var form = document.getElementsByName('login');" +
                                "form[0].submit();};"
                        );
                        send = true;
                    }
                }


            });
        }
    });
    }
}

Aquí está mi LogCat:

java.lang.RuntimeException: Unable to start activity ComponentInfo{com.timbremer.iimv/com.timbremer.iimv.MainActivity}: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
        at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2215)
        at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2265)
        at android.app.ActivityThread.access$800(ActivityThread.java:145)
        at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1206)
        at android.os.Handler.dispatchMessage(Handler.java:102)
        at android.os.Looper.loop(Looper.java:136)
        at android.app.ActivityThread.main(ActivityThread.java:5081)
        at java.lang.reflect.Method.invokeNative(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:515)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:781)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
        at dalvik.system.NativeStart.main(Native Method)
 Caused by: java.lang.IllegalStateException: You need to use a Theme.AppCompat theme (or descendant) with this activity.
        at android.support.v7.app.ActionBarActivityDelegate.onCreate(ActionBarActivityDelegate.java:111)
        at android.support.v7.app.ActionBarActivityDelegateICS.onCreate(ActionBarActivityDelegateICS.java:58)
        at android.support.v7.app.ActionBarActivity.onCreate(ActionBarActivity.java:98)
        at com.timbremer.iimv.MainActivity.onCreate(MainActivity.java:36)

Gracias por tu ayuda.