title: TwitterSession must not be null
body: <p>I have used this code to compose tweet but getting TweitterSession error. Here, I attached log, please help me to resolved this issue.</p>
  
  <p>//In Application Class</p>
  
  <pre><code>TwitterConfig config = new TwitterConfig.Builder(this)
                      .logger(new DefaultLogger(Log.DEBUG))//enable logging when app is in debug mode
                      .twitterAuthConfig(new TwitterAuthConfig("ConsumerKey", "ConsumerSecret"))//pass the created app Consumer KEY and Secret also called API Key and Secret
                      .debug(true)//enable debug mode
                      .build();
  
              //finally initialize twitter with created configs
  
              Twitter.initialize(config);
  </code></pre>
  
  <p>//OnClick on button</p>
  
  <pre><code>final TwitterSession session = TwitterCore.getInstance().getSessionManager().getActiveSession();
              final Intent intent = new ComposerActivity.Builder(MainActivity.this)
                      .session(session)
                      .text("Love where you work")
                      .hashtags("#twitter")
                      .createIntent();
              startActivity(intent);
  </code></pre>
  
  <p>Logs::</p>
  
  <pre><code>TwitterSession must not be null
          at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2450)
          at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2510)
          at android.app.ActivityThread.-wrap11(ActivityThread.java)
          at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1363)
          at android.os.Handler.dispatchMessage(Handler.java:102)
          at android.os.Looper.loop(Looper.java:148)
          at android.app.ActivityThread.main(ActivityThread.java:5461)
          at java.lang.reflect.Method.invoke(Native Method)
          at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:726)
          at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:616)
       Caused by: java.lang.IllegalArgumentException: TwitterSession must not be null
          at com.twitter.sdk.android.tweetcomposer.ComposerActivity$Builder.session(ComposerActivity.java:95)
          at com.example.inextrix.twittereazydemo.MainActivity.onCreate(MainActivity.java:51)
          at android.app.Activity.performCreate(Activity.java:6251)
  </code></pre>