Exclusion filter does not filter out 'null'

[mkuthan]

The exclusion filter does not filter out 'null' value. It is independent of the visualisation type.

Scatter plot:
https://turnilo.app/#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

Grid:
https://turnilo.app/#wiki/4/N4IgbglgzgrghgGwgLzgFwgewHYgFwgDmAThACYgA0408SqGOAygKZobaFT7YwILUMAWxbIcLfCACiaAMYB6AKoAVAMJUQAMwgI0LYtzwBtUGgCeABwkFhE6sRabJtjbYAK+rGUMmQZGMToWLgEbgCMAJoaUHoW+AC0YYKW1iAI6CwxIAC+ALrZlKYpkjGknBoOTgSyEOYAcnAiGnCyjCEgELjUYIgwmfhGILz8ILnU2Jho+GjEfXnUUBZIaD5FViUznYQaZBAi2FDBkjX1jXYgUJjEU3iglZJwZGQsFMnrBFCe/dS7Dq1HBGeUFkLGwu3K1CspEwFAIOWoSCEtXwAFYAAzzC5fVYgSr6UEgh5PF4aTRXITofBrVLPTRwPhTbq9VLwkDmd4gERwWAOeF3Rz47CEwEsBBsEnUMnECk3amSWn03QaHoIPqSVns1JcnkSTEWTrYF4AET2oMOOB8YxA+uwhrITCuNxAj2eFGyQA=

[adrianmroz-allegro]

We don't have any guarantees about values inside string dimensions. They can hold null or any other value.

Right now we eagerly convert all values to string here
We should do this more lazy, so we keep original values and show stringified version on UI. Of course that will lead to confusion if non-string value evaluates to existing string value. But I thinks that's on dataset administrator.