Product and version
FileMaker Pro 14.0.5
OS and version
iMac Retina 5K 27'' late 2014
If a value list is based on a field which can be empty, the Windows version is showing the second field even if the first is empty. This is not the case with the Mac version AND this was not the case with FileMaker 13.0v5 on Windows.
How to replicate
Create two fields, typically an ID and a Name
Create a value list based on the first but showing only the second field
Add some record with and without ID
On a layout of a related table, format the foreign key as a Pop-menu using this value list.
Only the second field's values where an ID was entered should currently appear on the pop menu.
Create a third field, calculation, populating that copy the second field only if the first is not empty.