`KeyError: "'rcp' is not a valid dimension or coordinate"` when running with non-RCP spec

[kemccusker]

This is probably related to Merge Request #44.
When calling with a non-RCP configuration, emissions_scenarios should be None and we should not be selecting anything with an rcp dimension.

Traceback (most recent call last):
  File "/Users/kellymccusker/Dropbox (Rhodium Group)/Kelly Workspace/ClimateImpactLab/analysis/ClimateImpactLab/Impacts/TESTINSTALL/dscim-epa/damage_fun_runs/command_line_scc.py", line 461, in <module>
    epa_sccs(sector,
  File "/Users/kellymccusker/Dropbox (Rhodium Group)/Kelly Workspace/ClimateImpactLab/analysis/ClimateImpactLab/Impacts/TESTINSTALL/dscim-epa/damage_fun_runs/command_line_scc.py", line 288, in epa_sccs
    df_single_scc, df_single_gcnp, meta = epa_scc(sector = sector,
  File "/Users/kellymccusker/Dropbox (Rhodium Group)/Kelly Workspace/ClimateImpactLab/analysis/ClimateImpactLab/Impacts/TESTINSTALL/dscim-epa/damage_fun_runs/command_line_scc.py", line 223, in epa_scc
    df = menu_item_global.uncollapsed_discount_factors
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/descriptors.py", line 18, in __get__
    setattr(instance, self.__func__.__name__, self.__func__(instance))
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/menu/decorators.py", line 26, in save_wrap
    out = func(self, *args, **kwargs)
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/menu/main_recipe.py", line 1354, in uncollapsed_discount_factors
    self.global_consumption_no_pulse / pop
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/descriptors.py", line 18, in __get__
    setattr(instance, self.__func__.__name__, self.__func__(instance))
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/menu/decorators.py", line 26, in save_wrap
    out = func(self, *args, **kwargs)
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/menu/main_recipe.py", line 968, in global_consumption_no_pulse
    fair_control = self.climate.fair_control
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/menu/simple_storage.py", line 226, in fair_control
    ds = self.anomalies[[f"control_{var}" for var in self.anomaly_vars]]
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/descriptors.py", line 18, in __get__
    setattr(instance, self.__func__.__name__, self.__func__(instance))
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/dscim/menu/simple_storage.py", line 200, in anomalies
    anomaly = anomaly.sel(rcp=self.emission_scenarios)
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/xarray/core/dataset.py", line 2533, in sel
    query_results = map_index_queries(
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/xarray/core/indexing.py", line 175, in map_index_queries
    grouped_indexers = group_indexers_by_index(obj, indexers, options)
  File "/Users/kellymccusker/opt/miniconda3/envs/dscim-epa/lib/python3.9/site-packages/xarray/core/indexing.py", line 139, in group_indexers_by_index
    raise KeyError(f"{key!r} is not a valid dimension or coordinate")
KeyError: "'rcp' is not a valid dimension or coordinate"