Dont throw exception if admin is null

For policy_suspend_packages(or for other policies which are not user
restriction) admin component comes to be null always when
fetched from DPMS and the code changed as part of this change used to
throw exception. So handling this case to show generic learn more link
in policy transparency dialog which opens settings showing list of all
admins, if admin details are not found.

Bug: 203564700
Test: com.android.cts.devicepolicy.MixedProfileOwnerTest#testSuspendPackage
Change-Id: Ib3b4490eaa11ceab53f0004f4b7d089f3c0ba4fb

packages/SettingsLib/src/com/android/settingslib/enterprise/ActionDisabledLearnMoreButtonLauncher.java

@@ -52,7 +52,6 @@ public abstract class ActionDisabledLearnMoreButtonLauncher {
     public final void setupLearnMoreButtonToShowAdminPolicies(Context context,
             int enforcementAdminUserId, EnforcedAdmin enforcedAdmin) {
         requireNonNull(context, "context cannot be null");
-        requireNonNull(enforcedAdmin, "enforcedAdmin cannot be null");
 
         // The "Learn more" button appears only if the restriction is enforced by an admin in the
         // same profile group or by the device owner. Otherwise the admin package and its policies
@@ -132,7 +131,7 @@ public abstract class ActionDisabledLearnMoreButtonLauncher {
     }
 
     private void showAdminPolicies(Context context, EnforcedAdmin enforcedAdmin) {
-        if (enforcedAdmin.component != null) {
+        if (enforcedAdmin != null && enforcedAdmin.component != null) {
             launchShowAdminPolicies(context, enforcedAdmin.user, enforcedAdmin.component);
         } else {
             launchShowAdminSettings(context);