Resolve issues caused by actual `None` value in dictionary variable

## Motivation  

- There are type-related issues at runtime caused by actual `None` values being present in dictionary-type variables.
- As a temporary measure, the affected code can be modified using `or` operator instead of `get` with default value.
- In the long term, these dictionary types should be converted to Pydantic types to explicitly generate correct default values.

JIRA Issue: BA-1953

The issue names no files, tests, or entry points. Start by locating dictionary-type variables that can contain actual None values and identifying their runtime type failures; done requires converting the affected dictionary types to Pydantic types with correct defaults.

Written by the indexing model from the issue text.