Merge remote-tracking branch 'me/generic-part-bdry' into mpi-distribute

Author: majosm

meshmode/mesh/__init__.py

@@ -1072,11 +1072,15 @@ def set_if_not_present(name, from_name=None):
 
     @property
     def ambient_dim(self):
+        if not self.groups:
+            return None
         from pytools import single_valued
         return single_valued(grp.nodes.shape[0] for grp in self.groups)
 
     @property
     def dim(self):
+        if not self.groups:
+            return None
         from pytools import single_valued
         return single_valued(grp.dim for grp in self.groups)