Ensure that cached_markdown_version is not nil

lib/gitlab/markdown_cache/active_record/extension.rb

@@ -39,7 +39,7 @@ module Gitlab
 
         def save_markdown(updates)
           return unless persisted? && Gitlab::Database.read_write?
-          return if cached_markdown_version < cached_markdown_version_in_database
+          return if cached_markdown_version.to_i < cached_markdown_version_in_database.to_i
 
           update_columns(updates)
         end

spec/lib/gitlab/markdown_cache/active_record/extension_spec.rb

@@ -228,4 +228,16 @@ RSpec.describe Gitlab::MarkdownCache::ActiveRecord::Extension do
       thing.refresh_markdown_cache!
     end
   end
+
+  context 'when persisted cache is nil' do
+    before do
+      thing.update_column(:cached_markdown_version, nil)
+    end
+
+    it 'does not save the generated HTML' do
+      expect(thing).to receive(:update_columns)
+
+      thing.refresh_markdown_cache!
+    end
+  end
 end