Add title to file browser cascade dialog in Id output directory selec… (

#1520)

* Add title to file browser cascade dialog in Id output directory selection, and safeguard against null description elsewhere

* Update CHANGELOG.md

Describe 1519 issue/fix

CHANGELOG.md

@@ -8,7 +8,8 @@ v4.6
 ======
 - Fix issue [#1494](https://github.com/opensim-org/opensim-gui/issues/1494): Changing muscle path color throws exception.
 - Fix issue [#1493](https://github.com/opensim-org/opensim-gui/issues/1493): Rotating experimental data fails or results an unusable file.
-- Fix issue [#1516](https://github.com/opensim-org/opensim-gui/issues/1516): Chains of Physical offset frames ignored when displaying GeometryPath 
+- Fix issue [#1516](https://github.com/opensim-org/opensim-gui/issues/1516): Chains of Physical offset frames ignored when displaying GeometryPath
+- Fix issue [#1519](https://github.com/opensim-org/opensim-gui/issues/1519): Exception thrown when browsing for output folder in Inverse Dynamics Tool dialog
 
 v4.5
 ======