Remove Empty Values from Parameter Sync

If an element is modified and the value of a synced parameter changes to blank, the parameter sync tool should empty this value instead of holding on to the previous value. There are a few instances I have noticed this not being the case.

One of them is when you are synchronizing insulation and/or liner thickness with another parameter. If the insulation/liner thickness is applied and then removed from an MEP Fabrication Ductwork/Pipework category element, the value of that thickness remains when it should be removed.

Another instance is when you are synchronizing a duct category's width/depth/diameter parameters. When you change a rectangular duct to a round duct, the width and depth parameters are still filled in when they should be blank. Also, when you change a round duct to a rectangular duct, the diameter parameter is still filled in when it should be blank.