Prevent error on publish check in create_log_entries_from_revisions (#6628)

Fixes #6498

CHANGELOG.txt

@@ -7,6 +7,7 @@ Changelog
  * Fix: Updated project template migrations to ensure that initial homepage creation runs before addition of locale field (Dan Braghis)
  * Fix: Restore ability to use translatable strings in `LANGUAGES` / `WAGTAIL_CONTENT_LANGUAGES` settings (Andreas Morgenstern)
  * Fix: Allow `locale` / `translation_of` API filters to be used in combination with search (Matt Westcott)
+ * Fix: Prevent error on `create_log_entries_from_revisions` when checking publish state on a revision that cannot be restored (Kristin Riebe)
 
 
 2.11.2 (17.11.2020)

CONTRIBUTORS.rst

@@ -486,6 +486,7 @@ Contributors
 * Naglis Jonaitis
 * Luis Nell
 * Andreas Morgenstern
+* Kristin Riebe
 
 Translators
 ===========

docs/releases/2.11.3.rst

@@ -16,6 +16,7 @@ Bug fixes
  * Updated project template migrations to ensure that initial homepage creation runs before addition of locale field (Dan Braghis)
  * Restore ability to use translatable strings in ``LANGUAGES`` / ``WAGTAIL_CONTENT_LANGUAGES`` settings (Andreas Morgenstern)
  * Allow ``locale`` / ``translation_of`` API filters to be used in combination with search (Matt Westcott)
+ * Prevent error on ``create_log_entries_from_revisions`` when checking publish state on a revision that cannot be restored (Kristin Riebe)
 
 
 Upgrade considerations

wagtail/core/management/commands/create_log_entries_from_revisions.py

@@ -60,7 +60,10 @@ class Command(BaseCommand):
                         comparison = get_comparison(revision.page.specific, previous_revision_as_page, current_revision_as_page)
                         has_content_changes = len(comparison) > 0
 
-                    if current_revision_as_page.live_revision_id == previous_revision.id:
+                    if (
+                        current_revision_as_page is not None
+                        and current_revision_as_page.live_revision_id == previous_revision.id
+                    ):
                         # Log the previous revision publishing.
                         self.log_page_action('wagtail.publish', previous_revision, True)