Is there an existing issue for this?

• I have searched the existing issues

What happened?

When the Site directory is a custom directory Sites/MySite (not the default directory Portals/[portalid] )
When working with Themes, an error occurs at the CreateThumbnail constructor in ThemesController

The current code strImage.Substring(strImage.IndexOf("portals\\") causes an error because "portals\\" does not exist in the path
Fix:
Replace the line strThumbnail = Globals.ApplicationPath + "/" + strThumbnail.Substring(strThumbnail.IndexOf("portals\\"));
with the line: strImage = strImage.Substring(Globals.ApplicationMapPath.Length);

Fix:
Replace the line strThumbnail = Globals.ApplicationPath + "/" + strThumbnail.Substring(strThumbnail.IndexOf("portals\\"));
by the line strThumbnail = strThumbnail.Substring(Globals.ApplicationMapPath.Length);

Steps to reproduce?

1. Create a new Site, in the Site Directory section, enter a custom folder name, for example "Sites/MYSITE"
   
   By default, the Site folder will be Portals/[PortalID], but I have a habit of changing this folder
2. Copy any Theme set to the "Sites/MYSITE-System/Skins" folder
3. Go to PersonalBar -> Themes and you will get an error
   Go to settings for any page and you will also get an error

Current Behavior

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Expected Behavior

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Relevant log output

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Anything else?

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Affected Versions

9.13.6 (latest release)

What browsers are you seeing the problem on?

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Code of Conduct

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