CDRIVER-3933 Reinit reply in estimatedDocumentCount for NamespaceNotFound (#766)

Author: benjirewis

src/libmongoc/src/mongoc/mongoc-collection.c

@@ -909,6 +909,9 @@ mongoc_collection_estimated_document_count (
          /* Collection does not exist. From spec: return 0 but no err:
           * https://github.com/mongodb/specifications/blob/master/source/crud/crud.rst#estimateddocumentcount
           */
+         if (reply) {
+            bson_reinit (reply);
+         }
          memset (error, 0, sizeof *error);
          count = 0;
          GOTO (done);

src/libmongoc/tests/unified/operation.c

@@ -817,12 +817,7 @@ operation_estimated_document_count (test_t *test,
       val = bson_val_from_int64 (op_ret);
    }
 
-   /* CDRIVER-3933 Remove special case for 0 count. */
-   if (op_ret == 0) {
-      result_from_val_and_reply (result, val, NULL, &op_error);
-   } else {
-      result_from_val_and_reply (result, val, &op_reply, &op_error);
-   }
+   result_from_val_and_reply (result, val, &op_reply, &op_error);
 
    ret = true;
 done: