API endpoint /v4/reloadtask/<taskId>/start not handling empty PUT bodies well

[mountaindude]

Describe the bug
Butler throws an error when calling this API with an empty JSON body.
Passing in an empty array [] works.

To Reproduce

curl -X "POST" "http://butler-host:8080/v4/reloadtask/cd3f1f3b-affa-4da5-b678-57b538e944d0/start" \
     -H 'X-HTTP-Method-Override: PUT' \
     -H 'content-type: application/json' \
     -H 'accept: application/json' \
     -d $'{}'

results in error.

Expected behavior
The API should be tolerant to an empty body or an empty array.