[User Switcher] Set default value if setting null.

Copies the logic of user manager which defaults to the device resources
in order to determine if user switcher is enabled by default.

Fixes: 254240785
Test: Added a unit test.
Test: wipe device. Skip setup. Open user switcher, observe that there
should be an add button in the fullscreen user switcher.

Change-Id: I0864de61e7bb9dd7436082f2bf486cf4887a192a

packages/SystemUI/src/com/android/systemui/user/data/repository/UserRepository.kt

@@ -242,7 +242,15 @@ constructor(
             val isUserSwitcherEnabled =
                 globalSettings.getIntForUser(
                     Settings.Global.USER_SWITCHER_ENABLED,
-                    0,
+                    if (
+                        appContext.resources.getBoolean(
+                            com.android.internal.R.bool.config_showUserSwitcherByDefault
+                        )
+                    ) {
+                        1
+                    } else {
+                        0
+                    },
                     UserHandle.USER_SYSTEM,
                 ) != 0
 

packages/SystemUI/tests/src/com/android/systemui/user/data/repository/UserRepositoryImplTest.kt

@@ -94,6 +94,24 @@ class UserRepositoryImplTest : SysuiTestCase() {
         )
     }
 
+    @Test
+    fun userSwitcherSettings_isUserSwitcherEnabled_notInitialized() = runSelfCancelingTest {
+        underTest = create(this)
+
+        var value: UserSwitcherSettingsModel? = null
+        underTest.userSwitcherSettings.onEach { value = it }.launchIn(this)
+
+        assertUserSwitcherSettings(
+            model = value,
+            expectedSimpleUserSwitcher = false,
+            expectedAddUsersFromLockscreen = false,
+            expectedUserSwitcherEnabled =
+                context.resources.getBoolean(
+                    com.android.internal.R.bool.config_showUserSwitcherByDefault
+                ),
+        )
+    }
+
     @Test
     fun refreshUsers() = runSelfCancelingTest {
         underTest = create(this)