ID 482037 - Custom Blend modes trigger Convert Layers dialog

Problem summary
Custom Blend modes trigger Convert Layers dialog

Customer reported version
Mari 4.7v3

Customer reported platform
Multiple

Steps to reproduce

1) Register a custom Blend Mode during launch

2) Create a new project 

3) In the Node Graph, create a Merge node

4) Save the project and close Mari

5) Relaunch Mari and open the project

Expected behaviour
The project should open.

Actual behaviour
The Convert Layers dialog appears when opening the project.

Workaround
Unknown.

Reproduced by support
This bug has been reproduced in:
Mari 4.7v3 - Windows 10 - CentOS 7.7

Unable to reproduce bug in:
Mari 4.7v2 - Windows 10 - CentOS 7.7

Earliest version tested
Mari 4.7v2 - This issue doesn't appear in this version and has regressed