Issues with tool reset after the "Clear" button

[aagamrshah]

-[ ] The clear button does not reset the progress bar
-[ ] If one presses the clear button after uploading a spectrum and then presses clear again, the tool crashes
-[ ] If one presses the clear button after uploading a spectrum and then tries to upload a new spectrum, the tool returns an error: 'NoneType' object has no attribute 'widget'