Make benchmark download cache-safe

app.js

@@ -1525,7 +1525,7 @@ function parseMetricMs(text) {
 function renderBenchmarkResults() {
   elements.resultsBody.replaceChildren();
   elements.copyResultsButton.disabled = state.benchmarkResults.length === 0;
-  elements.downloadResultsButton.disabled = state.benchmarkResults.length === 0;
+  if (elements.downloadResultsButton) elements.downloadResultsButton.disabled = state.benchmarkResults.length === 0;
   elements.clearResultsButton.disabled = state.benchmarkResults.length === 0;
   renderBenchmarkSummary();
   if (state.benchmarkResults.length === 0) {
@@ -2562,7 +2562,7 @@ elements.copyResultsButton.addEventListener("click", () => {
     logEvent(payload);
   }
 });
-elements.downloadResultsButton.addEventListener("click", downloadBenchmarkJson);
+elements.downloadResultsButton?.addEventListener("click", downloadBenchmarkJson);
 elements.clearResultsButton.addEventListener("click", () => {
   cancelMicSeries();
   clearBenchmarkTimeout();