Handle missing repo count gracefully

Let's handle this case gracefully and skip displaying the number of repositories
when they're not available.

Similarly let's add a check to see if we should pluralize the `repository` noun
or not.

Co-authored-by: Shati Patel <shati-patel@github.com>

extensions/ql-vscode/src/remote-queries/export-results.ts

@@ -106,7 +106,9 @@ async function exportResultsToGist(
  */
 const buildGistDescription = (query: RemoteQuery, analysesResults: AnalysisResults[]) => {
   const resultCount = sumAnalysesResults(analysesResults);
-  return `${query.queryName} (${query.language}) ${resultCount} results (${query.numRepositoriesQueried} repositories)`;
+  const repositoryLabel = `${query.numRepositoriesQueried} ${query.numRepositoriesQueried === 1 ? 'repository' : 'repositories'}`;
+  const repositoryCount = query.numRepositoriesQueried ? repositoryLabel : '';
+  return `${query.queryName} (${query.language}) ${resultCount} results (${repositoryCount})`;
 };
 
 /**