On Results Tab, "Set Path to DView in Preferences" isn't "registered" until you switch tabs

[jmarrec]

Issue overview

If you haven't set the path to DView in Preferences, it displays a button on the Results tab to set it.
But you have to change to another tab and back to the Results tab so that it's processed correctly and the button changes to "Open in DView". This isn't a huge deal since a user will generally have to do this only once.

Steps to Reproduce

1. Go to Preferences > External Tools > Clear path to DVIew
2. Go to Results tab when you have a model with a successful run
3. CLick "Set Path to DView" and set it

4. It isn't registered

5. Switch to another tab then back to the Results tab, now it's fine

Possible Solution

Details

Environment

Some additional details about your environment for this issue (if relevant):

• Platform (Operating system, version): Ubuntu 18.04
• Version of OpenStudioApplication (if using an intermediate build, include SHA): 1.0.0-rc1, 0845fd1

Context

[jmarrec]

This was done in https://github.com/NREL/OpenStudioApplication/pull/33/files#diff-acf859aed04b90ae7e4ceef885950f48, and it will definitely not work on mac, period, in its current form either