When sending a delete, null may not be used

When sending a delete, null may not be used for the data parameter or a
ArgumentNullException will be thrown. In this case we send an empty
string.
Revert "When sending a delete, null may not be used"

This reverts commit 7afe20d7831aab40f3b5f85a3729b23784db60d3.
When sending a delete, null may not be used