[Journeys] Fix crash when initing with null activity

This seems to happen if we create the coordinator post-destroy.

(cherry picked from commit 80d1a6a)

Bug: 1366905
Change-Id: Icfdeb9219c59b6620ee3f8ec29727983c4f4b043
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3915271
Commit-Queue: Patrick Noland <pnoland@chromium.org>
Reviewed-by: Matthew Jones <mdjones@chromium.org>
Cr-Original-Commit-Position: refs/heads/main@{#1050651}
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3917011
Commit-Queue: Krishna Govind <govind@chromium.org>
Owners-Override: Krishna Govind <govind@chromium.org>
Bot-Commit: Rubber Stamper <rubber-stamper@appspot.gserviceaccount.com>
Reviewed-by: Krishna Govind <govind@chromium.org>
Cr-Commit-Position: refs/branch-heads/5304@{chromium#152}
Cr-Branched-From: 5d7b1fc-refs/heads/main@{#1047731}

chrome/android/java/src/org/chromium/chrome/browser/ui/RootUiCoordinator.java

@@ -842,6 +842,7 @@ protected IncognitoReauthCoordinatorFactory getIncognitoReauthCoordinatorFactory
     }
 
     private void initHistoryClustersCoordinator(Profile profile) {
+        if (mActivity == null) return;
         if (ChromeFeatureList.isEnabled(ChromeFeatureList.HISTORY_JOURNEYS)) {
             HistoryClustersDelegate historyClustersDelegate = new HistoryClustersDelegate() {
                 @Override