Check if new_ds_name registered to MetadataCatalog before removing

Summary:
As title, sometimes new_ds_name is not registered so it crashes the program when calling remove(). Adding a check.
A side effect to this is if it's not registered, get() method will register it first and then remove() will remove it from registery.

Reviewed By: ppwwyyxx

Differential Revision: D31049303

fbshipit-source-id: 149168fb89fd3b661b60717ff2aafa7a9bd52849

d2go/data/utils.py

@@ -150,7 +150,8 @@ class AdhocCOCODataset(AdhocDataset):
         metadata_dict["name"] = self.new_ds_name
         if "json_file" in metadata_dict:
             metadata_dict["json_file"] = tmp_file
-        MetadataCatalog.remove(self.new_ds_name)
+        if MetadataCatalog.get(self.new_ds_name):
+            MetadataCatalog.remove(self.new_ds_name)
         MetadataCatalog.get(self.new_ds_name).set(**metadata_dict)
 
     def cleanup(self):