Describe the bug

All PVWatts Battery configurations produce the error "exec fail(battery): If grid_outage is specified in any time step, crit_load must have length > 0 and values > 0
Simulation battwatts failed :exec fail(battery): If grid_outage is specified in any time step, crit_load must have length > 0 and values > 0" when attempting to specify a grid outage and a critical load. The same specification works with cmod_battery

To Reproduce

Steps to reproduce the behavior:

1. Open a PVWatts-Battery configuration
2. Specify a critical load
3. Specify a grid outage
4. Run the simulation and see the error

Expected behavior

Either we should remove the UI widgets from PVWatts-Battery, or the grid outage behavior should match the mainline battery configurations.

Operating System and Version

• Version 2021.12.02