Fix NPE if keyboard settings is launched by work apps

IME apps can request users to enable them by directly
launching the on-screen keyboard settings page.

If keyboard settings is launched by works apps, the
current userId would be work userId. There is no managed
profile for work user so the exception happened.

-. Use current userId if it's launched by work user
-. Use primary user info for personal fragment

Fix: 216395439
Test: Manual test with issue steps
Test: make RunSettingsRoboTests ROBOTEST_FILTER=AvailableVirtualKeyboardFragmentTest
Change-Id: Iea573922ee789d9932c0de05bf71179c4f005eeb