[Bug] GUI fails silently trying to set up a new instance if it doesn't have write permissions

[DasSkelett]

Background

• Operating System: Linux & macOS, might affect Windows as well
• CKAN Version: v1.30.1

Have you made any manual changes to your GameData folder (i.e., not via CKAN)?
No

Problem

Describe the bug
CKAN fails silently if it doesn't have write permissions to the KSP directory.
Exception can only be seen if run from terminal.

Steps to reproduce

• Install KSP as one user (or chown -R 1999:1999 <path to existing KSP>)
• Open CKAN as another user that doesn't have write access to the KSP directory
• Try to add this KSP instance to CKAN
• If you do this during the initial game instance selection dialog (if you have no default instance set), CKAN crashes completely, without any message
• If you do this while another instance is already loaded, using the "File > Manage game instances" option, the file selection dialog closes but nothing else happens.

Expected behavior
CKAN should show an error message that it can't setup its files due to permission problems

CKAN error code (if applicable):

System.UnauthorizedAccessException: Access to the path '/ram/Fake-1.11.1/CKAN' is denied. ---> System.IO.IOException: Keine Berechtigung
--- End of inner exception stack trace ---
at System.IO.FileSystem.CreateDirectory (System.String fullPath) [0x00191] in <673b2a9c49de4736b9b01249f8d6d6b1>:0
at System.IO.Directory.CreateDirectory (System.String path) [0x0002c] in <673b2a9c49de4736b9b01249f8d6d6b1>:0
at ChinhDo.Transactions.FileManager.TxFileManager.CreateDirectory (System.String path) [0x0001b] in <bd256a5f4bd9434c90d5e776dca9de7b>:0
at CKAN.GameInstance.SetupCkanDirectories (System.Boolean scan) [0x0006e] in <bd256a5f4bd9434c90d5e776dca9de7b>:0
at CKAN.GameInstance..ctor (CKAN.Games.IGame game, System.String gameDir, System.String name, CKAN.IUser user, System.Boolean scan) [0x0007e] in <bd256a5f4bd9434c90d5e776dca9de7b>:0
at CKAN.GameInstanceManager.AddInstance (System.String path, System.String name, CKAN.IUser user) [0x00053] in <bd256a5f4bd9434c90d5e776dca9de7b>:0
at CKAN.ManageGameInstancesDialog.AddToCKANMenuItem_Click (System.Object sender, System.EventArgs e) [0x0005f] in <bd256a5f4bd9434c90d5e776dca9de7b>:0

System.UnauthorizedAccessException: Access to the path '/Applications/Ksp/Kerbal Space Program 181/CKAN' is denied. ---> System.IO.IOException: Permission denied

[HebaruSan]

Thanks!