Refuse when user profile path includes an exclamation mark

[Pyker]

The launcher should display an error and immediately exit, if the user profile path includes an exclamation mark (!), since that causes issues with Java misinterpreting it as a path to a JAR and a path inside said JAR file.

This is always a problem even if the user installs the launcher to a different folder, since the launcher always checks %APPDATA%\.technic\settings.json so it can determine where it's installed. This should not be a problem in portable mode, since it checks the current folder and uses that directly, instead of checking appdata.

[github-actions]

This issue is stale because it has been open for 90 days with no activity.