From the error message, it looks like you've got an uninitialized EMS variable. You'll need to provide an initialization. Uninitialized variables were previously allowed, but that was changed for version 8.6. Here's the issue that was raised:
https://github.com/NREL/EnergyPlus/is...
And the pull request that made the change is here:
https://github.com/NREL/EnergyPlus/pu...
That link is failing to load for me right now (the dreaded GitHub angry unicorn), but the change is listed in the changelog here. It's listed under "Defects Repaired".