Android: More robust check for whether to sync channels

This changes channel syncing to happen when the operating system is
Android TV rather than when TvMainActivity is launched. (You can run
TvMainActivity on a phone by specifying a launch activity manually
in Android Studio, which I do sometimes for testing purposes. Without
this change, you get an exception when channel syncing runs.)

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/ui/main/TvMainActivity.java

@@ -59,8 +59,6 @@ public final class TvMainActivity extends FragmentActivity implements MainView
     {
       StartupHandler.HandleInit(this);
     }
-    // Setup and/or sync channels
-    TvUtil.scheduleSyncingChannel(getApplicationContext());
   }
 
   @Override

Source/Android/app/src/main/java/org/dolphinemu/dolphinemu/utils/StartupHandler.java

@@ -27,6 +27,10 @@ public final class StartupHandler
     // Ask the user if he wants to enable analytics if we haven't yet.
     Analytics.checkAnalyticsInit(parent);
 
+    // Set up and/or sync Android TV channels
+    if (TvUtil.isLeanback(parent))
+      TvUtil.scheduleSyncingChannel(parent);
+
     String[] start_files = null;
     Bundle extras = parent.getIntent().getExtras();
     if (extras != null)