Fix home calculation Fixes #46821 (#46836)

Fixes #46821

#46349 was part of a set of changes to support containers that don't have HOME set to anything. Unfortunately, DOTNET_CLI_HOME (which is what we use instead) may not be set to things in other environments, notably with a zip install. Since Path.Combine is used, this led to a null pointer exception.

This changes it to skip copying the nuget.config if DOTNET_CLI_HOME is not defined to avoid an error. It's fine to not error in that case since it's best effort anyway.

Author: Forgind

src/Cli/dotnet/SudoEnvironmentDirectoryOverride.cs

@@ -33,16 +33,19 @@ public static void OverrideEnvironmentVariableToTmp(ParseResult parseResult)
             if (!OperatingSystem.IsWindows() && IsRunningUnderSudo() && IsRunningWorkloadCommand(parseResult))
             {
                 string sudoHome = PathUtilities.CreateTempSubdirectory();
-                var homeBeforeOverride = Path.Combine(Environment.GetEnvironmentVariable(CliFolderPathCalculator.DotnetHomeVariableName));
+                var homeBeforeOverride = Environment.GetEnvironmentVariable(CliFolderPathCalculator.DotnetHomeVariableName);
                 Environment.SetEnvironmentVariable(CliFolderPathCalculator.DotnetHomeVariableName, sudoHome);
 
-                CopyUserNuGetConfigToOverriddenHome(homeBeforeOverride);
+                if (homeBeforeOverride is not null)
+                {
+                    CopyUserNuGetConfigToOverriddenHome(homeBeforeOverride);
+                }
             }
         }
 
         /// <summary>
         /// To make NuGet honor the user's NuGet config file.
-        /// Copying instead of using the file directoy to avoid existing file being set higher permission
+        /// Copying instead of using the file directly to avoid existing file being set higher permission
         /// Try to delete the existing NuGet config file in "/tmp/dotnet_sudo_home/"
         /// to avoid different user's NuGet config getting mixed.
         /// </summary>