Unknown veg_ values cause issues in albedo decay methods

[micah-prime]

Unknown veg_ values in the config parse as a list of strings. This means that the date_method of albedo decay will fail when running with unknown veg_ config options

[scotthavens]

To be clear, this is happening when you add a veg_ option that isn't present in the topo.nc?

While this may be a pain for the operational release, is it worth the fix? Seems like the easier solution is to fix the configuration file?