Fix nil coercion updating storage size on project statistics

app/models/project_statistics.rb

@@ -54,7 +54,7 @@ class ProjectStatistics < ApplicationRecord
   end
 
   def update_storage_size
-    self.storage_size = repository_size + wiki_size + lfs_objects_size + build_artifacts_size + packages_size
+    self.storage_size = repository_size + wiki_size.to_i + lfs_objects_size + build_artifacts_size + packages_size
   end
 
   # Since this incremental update method does not call update_storage_size above,

changelogs/unreleased/ac-63020-typeerror-nil-can-t-be-coerced-into-integer.yml

+---
+title: Fix nil coercion updating storage size on project statistics
+merge_request: 29425
+author:
+type: fixed

spec/models/project_statistics_spec.rb

@@ -197,6 +197,18 @@ describe ProjectStatistics do
 
       expect(statistics.storage_size).to eq 9
     end
+
+    it 'works during wiki_size backfill' do
+      statistics.update!(
+        repository_size: 2,
+        wiki_size: nil,
+        lfs_objects_size: 3
+      )
+
+      statistics.reload
+
+      expect(statistics.storage_size).to eq 5
+    end
   end
 
   describe '.increment_statistic' do