Fix single-property config group display
Fix single-property config group display

In the case of numerical single-property config groups, the value would
sometimes display as 0 if the device sends property change notifications.
(e.g. NikonTi TIRF Position)

git-svn-id: 03a8048b5ee8463be5048a3801110fb50f378627@16402 d0ab736e-dc22-4aeb-8dc9-08def0aa14fd

kmdouglass/Micro-Manager,kmdouglass/Micro-Manager