azp: cli tool azexpand fix error for missing --local-repository switch (#542)

* unexpected null error due to returning a null task in implementation

Author: ChristopherHX

Diff for: src/Runner.Client/Program.cs

@@ -877,7 +877,7 @@ public Task<string> ReadFile(string repositoryAndRef, string path)
                 {
                     var reporoot = repositoryAndRef == null ? Path.GetFullPath(handle.Directory ?? ".") : (from r in handle.LocalRepositories where MatchRepository(r, repositoryAndRef) select Path.GetFullPath(r.Substring($"{repositoryAndRef}=".Length))).LastOrDefault();
                     if(string.IsNullOrEmpty(reporoot)) {
-                        return null;
+                        return Task.FromResult<string>(null);
                     }
                     return File.ReadAllTextAsync(Path.Join(reporoot, path), Encoding.UTF8);
                 }

Diff for: src/azure-pipelines-vscode-ext/CHANGELOG.md

@@ -1,6 +1,7 @@
 ### v0.2.9
 - Fix file picker of v0.2.8 to be usable
 - Fix variables in template parameter showing incorrect errors
+- Fix variables overridden in nested scopes showing incorrect errors
 
 ### v0.2.8
 - Suppress mapping schema errors while parsing if / each expressions