Filter demands to prevent 0/0 division error (#794)

* Filter demands to prevent 0/0 division error

* Detect dimensions dynamically

Author: tsmbland

src/muse/sectors/subsector.py

@@ -87,6 +87,14 @@ def aggregate_lp(
             timeslice_level=self.timeslice_level,
         )
 
+        # Further filer demands to only include commodities with positive unmet demand
+        # Some commodities may be lost here if capacity is already sufficient to meet
+        # demand
+        demands = demands.where(
+            demands.sum([dim for dim in demands.dims if dim != "commodity"]) > 0,
+            drop=True,
+        )
+
         if "dst_region" in demands.dims:
             msg = """
                 dst_region found in demand dimensions. This is unexpected. Demands