Problem

In Provider API scripts, we often check if a required value exists using if <value> is None checks:

However, this lets other falsy values (such as empty strings) to pass the test, which might cause issues like WordPress/openverse-catalog#1102

Description

Since non-None falsy values (empty strings, empty dictionaries) do not make sense as values for required parameters such as foreign landing url or url, we should replace the is None checks with if value checks.

Alternatives

The current solution with checks for None works in most cases, and the checks could be done in the MediaStore classes. However, it moves the check back in the ingestion process, and makes it longer unnecessarily.

Additional context

The template for provider scripts should be updated, too.