Updated null check for getting CompletionMatches so results or results.CompletionMatches could be null.

Author: dkattan

src/PowerShellEditorServices/Services/TextDocument/Handlers/CompletionHandler.cs

@@ -215,7 +215,7 @@ internal async Task<CompletionResults> GetCompletionsInFileAsync(
                 _logger,
                 cancellationToken).ConfigureAwait(false);
 
-            if (result is null || result.CompletionMatches.Count is 0)
+            if (!(result?.CompletionMatches?.Count > 0))
             {
                 return new CompletionResults(IsIncomplete: true, Array.Empty<CompletionItem>());
             }