Fix crash when default app settings is not available

When "system settings" method is used under P-, the app crashes because
the system does not have "change default" settings. This CL skips
when the system does not have such settings.

Bug: 1122907
Change-Id: I6133e83ee15074cd48bd4db6c098005428cb088b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2382895
Commit-Queue: Lijin Shen <lazzzis@google.com>
Reviewed-by: Pavel Yatsuk <pavely@chromium.org>
Cr-Commit-Position: refs/heads/master@{#802921}

chrome/browser/ui/android/default_browser_promo/java/src/org/chromium/chrome/browser/ui/default_browser_promo/DefaultBrowserPromoUtils.java

@@ -154,6 +154,9 @@ public class DefaultBrowserPromoUtils {
                     ChromeFeatureList.ANDROID_DEFAULT_BROWSER_PROMO, P_NO_DEFAULT_PROMO_STRATEGY);
             if (TextUtils.equals(promoOnP, "disabled")) {
                 return false;
+            } else if (TextUtils.equals(promoOnP, "system_settings")
+                    && !doesManageDefaultAppsSettingsActivityExist()) {
+                return false;
             }
         }