Fix duplicate entries in index.py

Author: amd-arsuresh

mlc/index.py

@@ -91,7 +91,7 @@ def add(self, meta, folder_type, path, repo):
 
         index = self.get_index(folder_type, unique_id)
 
-        if index != -1:
+        if index == -1:
             self.indices[folder_type].append({
                     "uid": unique_id,
                     "tags": tags,