ID 228807 - Save button is greyed out when using Export chan file on a Camera node

Problem summary

The save button when using Export chan file from a Camera node is greyed out.

Customer reported version
nuke.9.0v8

Steps to reproduce

1) Open Nuke

2) Create a Camera node

3) Click on the file icon  the file_menu knob, then Export chan file

4) The Chan File dialogue that opens has the Save button greyed out. You can press enter instead to save, even though the button is inactive.

Reproduced by support
This problem has been reproduced in:

Nuke 10.0v3 - Windows 10 - CentOS 6.7

Nuke 10.0v1 - Windows 10

Nuke 9.0v9 - Windows 10

Nuke 9.0v1 - Windows 10 CentOS 6.7

The issue did not occur in:

Nuke 8.0v6 - Windows 10 - CentOS 6.7 

Expected behaviour

For the Save button to be active

Actual behaviour
The Save button was greyed out, inactive.