incongruency between upload button disabled status and file input in config menu when canceling file choice

[taeyunmlee135]

Steps to replicate: (in Config menu - either Data Upload or Model Upload)

1. add a file (thus enabling the Upload button)
2. click "Choose File" again, but cancel the File Explorer popup before making a selection (input should switch back to saying "No file chosen" but Upload button stays enabled)

• the issue only occurs when a file is chosen and then no file is chosen (if the user cancels the initial popup without choosing a file the Upload button stays disabled)
• I believe that when step 2 happens, the file input no longer thinks a file has been selected, but the previously selected file is still preserved in the app's internal state somewhere and when the Upload button is clicked, the previously selected file gets uploaded
• I tested what happens when the Upload button is clicked in this state with an invalid (pdf) file, and got an error saying "Could not interpret model file. Upload canceled.", the same error that I would get if I just tried to upload a pdf file while the input showed the pdf file as chosen.
• to test the theory it would be best to follow the replication steps selecting a valid (not a pdf) model file for step 1, and see if the same error occurs. If so, the internal state preservation theory would be supported but if not, it would seem that the error would be caused by trying to upload no file, suggesting the problem lies in the Upload button staying enabled

[taeyunmlee135]

see pull request/branch 166 taeyun configtweaks for initial implementation introducing the bug