fixed created_at, created_on, updated_at, and update_on should check for value (patch from mike_pb, closes #242)
fixed created_at, created_on, updated_at, and update_on should check for value (patch from mike_pb, closes #242)

git-svn-id: 2f0e1b834f829f9d45d4005679b0d62d953a4cdf@1033 4396de85-42e0-4213-a939-0f47b466bcdf

morhekil/symfony,morhekil/symfony,morhekil/symfony