Save As does not work unless the file already exists.

[ghost]

Describe the bug Save as shows a message box if the target file does not exist.

Application: Brain Simulator

Module/Network: N/A

To Reproduce Steps to reproduce the behavior:

1. Open any network.
2. Select File => Save As.
3. Enter a name of another existing file to overwrite it.
4. Notice Save As works fine.
5. Now perform Save As again, this time with a name that does not exist.
6. Notice the message box below, indicating Save As won't work because the file was not found.

Expected behavior Save As should work unless the folder where you save the file cannot be written in, or it tries to overwrite a read-only file.

Screenshots If applicable, add screenshots to help explain your problem.

Desktop (please complete the following information):

• OS: Windows 10 Pro 20H2
• Version: 2021-04-24 master

Add any other context about the problem here.