Bug 6949: cannot remove owner from fund

Bug 6949: cannot remove owner from fund

The Javascript to remove an owner from a budget cleared the name from the screen, but did not remove
the actual value in the form, so when saving, the original owner was retained.

This patch adds the command to set the value to ''.

Signed-off-by: Katrin Fischer <Katrin.Fischer.83@web.de>
I could reproduce the bug on current master. Patch fixes the problem, fund
owners can now be added and removed without any problems.
Thx for providing a test plan!

Signed-off-by: Chris Cormack <chrisc@catalyst.net.nz>