[DatasetMigration] Migration fails if no source_params are set

[jsh2134]

If no source params are passed an error is returned

DatasetMigration.create(
    source_id=dataset$id,
    target_id=dataset$id,
    target_fields=fields
)

Error parsing API response
Error in value[[3L]](cond) : {"non_field_errors": ["No input provided"]}

WIth source_params

DatasetMigration.create(
    source_id=dataset$id,
    target_id=dataset$id,
    source_params=list(limit=1),
    target_fields=fields
)
# success

The NULL value must be sent incorrectly.

Oddly enough, if I pass source_params and no target_fields, we do not have this problem. So maybe the API serializer?

[jsh2134]

passing some dummy params will work

DatasetMigration.create(
    source_id=dataset$id,
    target_id=dataset$id,
    source_params=list(fake_kwarg=1),
    target_fields=fields
)