ID 390779 - Sharing a layer which has a procedural mask is resulting in a new shared layer with clamped mask values

Problem summary
Sharing a layer which has a procedural mask is resulting in a new shared layer with clamped mask values  

Customer reported version

Customer reported platform
rhel6

Steps to reproduce

1) Open Mari and the attached archive
2) Compare both of the channels

result: the mask is clamped

Original:                                                                              Shared:
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Expected behaviour
Both of the channels should look the same regardless of the mask/procedural use

Actual behaviour
The color values for the shared channel are clamped 

Workaround
Add a Clamp adjustment layer to the original Mask stack and share the layer afterwards.

Reproduced by support
This bug has been reproduced in:
4.5v1 - Windows 10 
3.3v1 - Windows 10
3.2v1 - Windows 10
2.6v5 - Windows 10

Earliest version tested
2.6v5 - This issue appears to be in all versions of the product