Bug 1527599 - Always show the Events section in about:telemetry for main pings. r=janerik

It can be confusing to have the "Events" section here for some "main" and
"main"-like pings, but not there for others. Keep it around even if there's no
data there to show.

We have a lovely display for "No data here, boss" so we might as well use it.

Differential Revision: https://phabricator.services.mozilla.com/D20564

--HG--
extra : moz-landing-system : lando

toolkit/content/aboutTelemetry.js

@@ -1859,7 +1859,13 @@ var Events = {
       let evts = aPayload.processes[value].events;
       return evts && Object.keys(evts).length > 0;
     });
-    setHasData("events-section", hasData);
+
+    // Don't specifically hide the events section if there's no data.
+    // It might be a "main" ping that needs to always show the section.
+    if (hasData) {
+      setHasData("events-section", true);
+    }
+
     if (Object.keys(events).length > 0) {
       const headings = [
         "timestampHeader",