Bug 22812: Fix new subscription with strict sql modes

Bug 22812: Fix new subscription with strict sql modes

With sql_strict_modes turned on, if you try to create a new subscription
you will get:
Incorrect integer value: '' for column '$INT_COLUMN' at row 1

Signed-off-by: Liz Rea <wizzyrea@gmail.com>
Signed-off-by: Marcel de Rooy <m.de.rooy@rijksmuseum.nl>
Signed-off-by: Michal Denar <black23@gmail.com>
Signed-off-by: Michal Denar <black23@gmail.com>
Signed-off-by: Katrin Fischer <katrin.fischer.83@web.de>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>