java/com/tailscale/ipn: run attachPeer on main thread

Signed-off-by: Elias Naur <mail@eliasnaur.com>

android/src/main/java/com/tailscale/ipn/App.java

@@ -160,11 +160,15 @@ public class App extends Application {
 	// attachPeer adds a Peer fragment for tracking the Activity
 	// lifecycle.
 	void attachPeer(Activity act) {
+		act.runOnUiThread(new Runnable() {
+			@Override public void run() {
 				FragmentTransaction ft = act.getFragmentManager().beginTransaction();
 				ft.add(new Peer(), PEER_TAG);
 				ft.commit();
 				act.getFragmentManager().executePendingTransactions();
 			}
+		});
+	}
 
 	boolean isChromeOS() {
 		return getPackageManager().hasSystemFeature("android.hardware.type.pc");