ID 473399 - Nuke crashes when an under operation Merge, Shuffle and Write node are viewed

Problem summary
Nuke crashes when an under operation Merge, Shuffle and Write node are viewed

Happens with both the Shuffle and Shuffle2 nodes, and the input into the Merge node has to be RGB, RGBA seems to work correctly

Customer reported version
nuke.12

Customer reported platform

linux

Steps to reproduce

1) Open Nuke

2) Create 3 Constant nodes
3) Create a Merge node, set the operation to under and set the connect the inputs A, B, and A2 to the Constant nodes

4) Connect a Shuffle node, and set the Alpha output to white

5) View the Shuffle node, Nuke sometimes crashes here

6) Create a Write node after the Shuffle node, Nuke should now crash

7) If it doesn't crash set the file knob on the Write node to crash.exr, it should now crash

8) If that doesn't work, disconnect the B input from the Merge node, Nuke should now crash

Expected behaviour

For nuke to display the results in the Viewer

Actual behaviour
Nuke crashes when Viewing the nodes

Workaround
Unknown. 

Reproduced by support
This bug has been reproduced in:

Nuke 13.0v1 - Windows 10, macOS 10.14

Nuke 12.2v1 - Windows 10

Nuke 12.1v1 - Windows 10

Nuke 12.0v1 - Windows 10, macOS 10.14 - regression

Unable to reproduce bug in:
Nuke 11.3v6 - Windows 10, macOS 10.14

Earliest version tested
Nuke 11.3v6 - This issue doesn't appear in this version and has regressed