ID 507824 - Loading a custom OCIO config with an empty fallback look entry causes errors

Problem summary
Loading a custom OCIO config with an empty fallback look entry causes errors
 
In versions 4.7 and earlier, if the referenced files in a sequence of looks cannot be found and the sequence ends in an empty entry, no error would be returned and the default View colorspace is used instead.
 
Customer reported version
Mari 4.8v2
 
Customer reported platform
RHEL 7
 
Steps to reproduce
 
1) Download and extract the attached OCIO configuration, 'Looks_error_config.zip'
 
2) Open an Example Project
 
3) Open Project Settings (File > Settings)
 
4) Set OCIO Config to Custom and load the downloaded config.ocio file
 
Expected behaviour
Mari should load the OCIO config without error. As the files referenced in the first two Looks of the default View's Looks sequence cannot be found, and the sequence ends in an empty entry, it should fallback to sRGB colorspace:
 

 
Actual behaviour
An error is returned when the config is loaded:
 

 
The View does not default to an sRGB colorspace/no View Transform is applied:
 

 
Workaround
Unknown.
 
Reproduced by support
This bug has been reproduced in:
Mari 5.0v2 - Windows 10 - CentOS 7.9
Mari 4.8v2 - Windows 10 - CentOS 7.9
Mari 4.8v1 - Windows 10 - CentOS 7.9 - regression
 
Unable to reproduce bug in:
Mari 4.7v7 - Windows 10 - CentOS 7.9
 
Earliest version tested
Mari 4.7v7 - This issue doesn't appear in this version and has regressed