Re #1790 formal change to kick-up the build.

herbert_core/utilities/classes/@hashable/private/to_hashable_array_.m

@@ -24,8 +24,8 @@
 % Recursively turn hashable fields values into array which defines
 % object's hash
 arr = cell (1,numel(field_names)*numel(obj)+1);
-arr{1} = uint8(class(obj))'; % ensure hashable array never empty 
-% and two different empty objects do not have the same hashes.
+arr{1} = uint8(class(obj))'; % ensure hashable array never empty and two
+% different empty objects of different classes do not have the same hashes.
 ic = 1;
 for j = 1:numel(obj)
     obj_tmp = obj(j);   % get cow pointer to j-th object to save expensive indexing