Uploading assets to a newly created page fails

[gerrit]

When on a new page form and trying to upload attachments it seems to work initially, but then the upload fails with status 500 and the following exception (using postgresql):

An exception occurred:

EXCEPTION:
ActiveRecord::StatementInvalid in assets#create

ERROR:
PGError: ERROR:  invalid input syntax for integer: ""
LINE 1: SELECT * FROM "pages" WHERE ("pages"."id" = '')  LIMIT 1
                                                    ^
: SELECT * FROM "pages" WHERE ("pages"."id" = '')  LIMIT 1