Fix IE issue when adding a blocktype (Bug 1341413)

The dynamic change of an input element from type=radio to type hidden
caused its value set to "" in IE.
It would be better to just hiding it instead of changing its type.

Change-Id: Id6a86f2e9a4bba2f2988e7fcbc3fac8f3d8468a2
Signed-off-by: Son Nguyen <son.nguyen@catalyst.net.nz>