(Fix) Storing tmdb via upload api

[Roardom]

Regression from #5371.

[what-the-diff]

PR Summary

• Streamlined Input Merging
  Updated usage of a single 'tmdb' input in place of both 'tmdb_movie_id' and 'tmdb_tv_id' to streamline validation function.

• Simplified Validation Rules
  Replaced Rule::when() checks with Rule::excludeIf() to simplify validation rules for various fields.

• Removed Null Attribute Function
  Extraneous function that ensured certain attributes had null values has been removed for improved efficiency in validation rules.