fixed loadData on YAML data file containing a linked field with a NULL value (closes #1288)
fixed loadData on YAML data file containing a linked field with a NULL value (closes #1288)

git-svn-id: 2f0e1b834f829f9d45d4005679b0d62d953a4cdf@3153 4396de85-42e0-4213-a939-0f47b466bcdf

morhekil/symfony,morhekil/symfony,morhekil/symfony