fix: if it's None

app.py

@@ -11,10 +11,10 @@ REVISION = os.getenv("REVISION")
 TARGET = os.getenv("TARGET")
 
 def func(hf_token, repo, revision, target_repo):
-    hf_token = hf_token if len(hf_token)>0 else HF_TOKEN
-    repo = repo if len(repo)>0 else REPO
-    revision = revision if len(revision)>0 else REVISION
-    target_repo = target_repo if len(target_repo)>0 else TARGET
+    hf_token = hf_token if hf_token is None else HF_TOKEN
+    repo = repo if repo is None  else REPO
+    revision = revision if revision is None  else REVISION
+    target_repo = target_repo if target_repo is None  else TARGET
     
     print('download the desired model locally ...')
     hf_api.snapshot_download(