Check for undefined, null or zero repositories

`undefined`, `null` and 0 will evaluate to `false` so if we only want to
display the repository count when these values are not present we can
check for a truthy value:

```
query.repositoryCount ? `(${pluralize(...)})` : '';
```

instead of checking explicitly:

```
query.repositoryCount !== undefined && query.repositoryCount !== null && query.repositoryCount != 0 ? `(${pluralize(...)})` : '';
```

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

@@ -110,7 +110,7 @@ export async function exportResultsToGist(
 const buildGistDescription = (query: RemoteQuery, analysesResults: AnalysisResults[]) => {
   const resultCount = sumAnalysesResults(analysesResults);
   const resultLabel = pluralize(resultCount, 'result', 'results');
-  const repositoryLabel = query.repositoryCount !== undefined ? `(${pluralize(query.repositoryCount, 'repository', 'repositories')})` : '';
+  const repositoryLabel = query.repositoryCount ? `(${pluralize(query.repositoryCount, 'repository', 'repositories')})` : '';
   return `${query.queryName} (${query.language}) ${resultLabel} ${repositoryLabel}`;
 };