marigold_ensemble integer fix (#389)

Code strengthening

Author: graemeniedermayer

src/backbone.py

@@ -42,6 +42,10 @@ def gather_ops():
                 c = get_cmd_opt(s, None)
             if c is not None:
                 ops[s] = c
+        # sanitize for integers.
+        for s in ['marigold_ensembles', 'marigold_steps']:
+            if s in ops:
+                ops[s] = int(ops[s])
         return ops