Don't crash when pressing Up button in WriteBlogPostActivity

Closes #587

briar-android/src/org/briarproject/android/blogs/WriteBlogPostActivity.java

@@ -7,6 +7,7 @@ import android.support.design.widget.TextInputLayout;
 import android.text.Editable;
 import android.text.TextWatcher;
 import android.view.KeyEvent;
+import android.view.MenuItem;
 import android.view.View;
 import android.widget.Button;
 import android.widget.EditText;
@@ -115,6 +116,17 @@ public class WriteBlogPostActivity extends BriarActivity
 		progressBar = (ProgressBar) findViewById(R.id.progressBar);
 	}
 
+	@Override
+	public boolean onOptionsItemSelected(MenuItem item) {
+		switch (item.getItemId()) {
+			case android.R.id.home:
+				onBackPressed();
+				return true;
+			default:
+				return super.onOptionsItemSelected(item);
+		}
+	}
+
 	@Override
 	public void injectActivity(ActivityComponent component) {
 		component.inject(this);