FIX: Wrap custom fields database statements in a transaction.

Kind of strange that we don't do it because a database statement
may fail and leave us in a weird state.

app/models/concerns/has_custom_fields.rb

@@ -194,9 +194,9 @@ module HasCustomFields
   def save_custom_fields(force = false)
     if force || !custom_fields_clean?
       dup = @custom_fields.dup
-
       array_fields = {}
 
+      ActiveRecord::Base.transaction do
         _custom_fields.reload.each do |f|
           if dup[f.name].is_a?(Array)
             # we need to collect Arrays fully before we can compare them
@@ -205,7 +205,7 @@ module HasCustomFields
             else
               array_fields[f.name] << f
             end
-        elsif dup[f.name].is_a? Hash
+          elsif dup[f.name].is_a?(Hash)
             if dup[f.name].to_json != f.value
               f.destroy!
             else
@@ -228,7 +228,7 @@ module HasCustomFields
           if fields.length == dup[field_name].length && fields.map(&:value) == dup[field_name]
             dup.delete(field_name)
           else
-          fields.each(&:destroy)
+            fields.each(&:destroy!)
           end
         end
 
@@ -244,6 +244,7 @@ module HasCustomFields
             )
           end
         end
+      end
 
       refresh_custom_fields_from_db
     end