Fix bin file exists check

[ScrubN]

The previous code was using a configuration property to check if the file exists, which would always pass because it defaults to true.

[ScrubN]

Force pushed the wrong branch, whoops.

[intbeam]

Checking if a file exists using File.Exists may cause unintended behavior because you can't know if the file gets immediately deleted between File.Exists and new FileStream (no matter how unlikely)

Use a try-catch for this specific type of issue, and only catch the specific exception (and not anything and especially not everything else)

try
{
}
catch(System.IO.FileNotFoundException ex)
{
}

CheckIfFileExists is a property on that class that affects the behavior of ShowDialog(), it doesn't do anything on its own. It prevents the user from entering a filename into the file text box that does not exist, so that should probably be set to true

[ScrubN]

If the user deletes the file in the 50 microseconds between the File.Exists check and the new FileStream and get a crash, then they deserve a medal. I see your point, but I disagree that it's relevant in this specific scenario, especially because I want to minimize diff changes to make it easier for TheCod3r to review the PR, and to avoid merge conflicts with #12.