[B+C] Update the call to BlockBurnEvent constructor for the getFireBlock method. Fixes BUKKIT-4231

See the details of the PR on the Bukkit PR, this is just an implementation detail.

As the constructor for BlockBurnEvent has changed to allow for the
getFireBlock method, the call has been updated.

BUKKIT-4231 - https://bukkit.atlassian.net/browse/BUKKIT-4231