Can not update submodule: module/tcl

[patrick-yingxi-pan]

I was running the following command on Ubuntu 18.04:

git clone --recursive https://github.com/The-OpenROAD-Project/TritonSizer.git

And encountered the following error from git:

error: Server does not allow request for unadvertised object 6efc06566b9ee1b8ed7645920b7f37226cc00643 Fetched in submodule path 'module/tcl', but it did not contain 6efc06566b9ee1b8ed7645920b7f37226cc00643. Direct fetching of that commit failed.