Reader: Remove redundant isEmpty check on preserved date

getDatePublished() already returns a non-null string via
StringUtils.notNullStr(), making the TextUtils.isEmpty guard
unnecessary.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: nbradbury

WordPress/src/main/java/org/wordpress/android/ui/reader/actions/ReaderPostActions.java

@@ -301,9 +301,7 @@ public void onResponse(JSONObject jsonObject) {
                     ReaderPost existingPost =
                             ReaderPostTable.getBlogPost(
                                     post.blogId, post.postId, true);
-                    if (existingPost != null
-                            && !TextUtils.isEmpty(
-                            existingPost.getDatePublished())) {
+                    if (existingPost != null) {
                         post.setDatePublished(
                                 existingPost.getDatePublished());
                     }