[Offline pages] Fixing a crash in URL change, when offline copy not present

components/offline_pages/offline_page_model.cc

Index: components/offline_pages/offline_page_model.cc
diff --git a/components/offline_pages/offline_page_model.cc b/components/offline_pages/offline_page_model.cc
index 26de71682ce1e198c734f2a4ddf91eb79dd7c6a2..98ff1c8728e4e8158d0d3ff7372a991d951e737f 100644
--- a/components/offline_pages/offline_page_model.cc
+++ b/components/offline_pages/offline_page_model.cc
@@ -477,8 +477,8 @@ void OfflinePageModel::BookmarkNodeChanged(
     const bookmarks::BookmarkNode* node) {
   // BookmarkNodeChanged could be triggered if title or URL gets changed. If
   // the latter, we need to invalidate the offline copy.
-  DCHECK(offline_pages_.count(node->id()) > 0);
-  if (offline_pages_[node->id()].url != node->url())
+  auto iter = offline_pages_.find(node->id());
+  if (iter != offline_pages_.end() && iter->second.url != node->url())
     DeletePageByBookmarkId(node->id(), DeletePageCallback());
 }