fix launch magisk manager from aicp_n-12.1 settings

--- 0-org/packages/apps/Settings/src/com/android/settings/SettingsActivity.java 2018-04-25 14:06:03.854590969 +0900
+++ 1-new/packages/apps/Settings/src/com/android/settings/SettingsActivity.java 2018-10-02 00:43:17.949797359 +0900
@@ -1117,8 +1117,7 @@
     private Fragment switchToFragment(String fragmentName, Bundle args, boolean validate,
             boolean addToBackStack, int titleResId, CharSequence title, boolean withTransition) {
         if (MAGISK_FRAGMENT.equals(fragmentName)) {
-            Intent magiskIntent = new Intent();
-            magiskIntent.setClassName("com.topjohnwu.magisk", "com.topjohnwu.magisk.SplashActivity");
+            Intent magiskIntent = getPackageManager().getLaunchIntentForPackage("com.topjohnwu.magisk");
             startActivity(magiskIntent);
             finish();
             return null;