MM-22619: check for nil plugins environment (#13901)

* MM-22619: check for nil plugins environment

Check if plugins were disabled before attempting to collect metrics and emit telemetry for same.

Fixes: https://mattermost.atlassian.net/browse/MM-22619

* Update app/diagnostics_test.go

app/diagnostics_test.go

@@ -68,7 +68,9 @@ func TestDiagnostics(t *testing.T) {
 		t.SkipNow()
 	}
 
-	th := Setup(t)
+	th := SetupWithCustomConfig(t, func(config *model.Config) {
+		*config.PluginSettings.Enable = false
+	})
 	defer th.TearDown()
 
 	type payload struct {
@@ -147,6 +149,58 @@ func TestDiagnostics(t *testing.T) {
 		}
 	})
 
+	// Plugins remain disabled at this point
+	t.Run("SendDailyDiagnosticsPluginsDisabled", func(t *testing.T) {
+		th.App.sendDailyDiagnostics(true)
+
+		var info []string
+		// Collect the info sent.
+	Loop:
+		for {
+			select {
+			case result := <-data:
+				assertPayload(t, result, "", nil)
+				info = append(info, result.Batch[0].Event)
+			case <-time.After(time.Second * 1):
+				break Loop
+			}
+		}
+
+		for _, item := range []string{
+			TRACK_CONFIG_SERVICE,
+			TRACK_CONFIG_TEAM,
+			TRACK_CONFIG_SQL,
+			TRACK_CONFIG_LOG,
+			TRACK_CONFIG_NOTIFICATION_LOG,
+			TRACK_CONFIG_FILE,
+			TRACK_CONFIG_RATE,
+			TRACK_CONFIG_EMAIL,
+			TRACK_CONFIG_PRIVACY,
+			TRACK_CONFIG_OAUTH,
+			TRACK_CONFIG_LDAP,
+			TRACK_CONFIG_COMPLIANCE,
+			TRACK_CONFIG_LOCALIZATION,
+			TRACK_CONFIG_SAML,
+			TRACK_CONFIG_PASSWORD,
+			TRACK_CONFIG_CLUSTER,
+			TRACK_CONFIG_METRICS,
+			TRACK_CONFIG_SUPPORT,
+			TRACK_CONFIG_NATIVEAPP,
+			TRACK_CONFIG_EXPERIMENTAL,
+			TRACK_CONFIG_ANALYTICS,
+			TRACK_CONFIG_PLUGIN,
+			TRACK_ACTIVITY,
+			TRACK_SERVER,
+			TRACK_CONFIG_MESSAGE_EXPORT,
+			// TRACK_PLUGINS,
+		} {
+			require.Contains(t, info, item)
+		}
+	})
+
+	// Enable plugins for the remainder of the tests.
+	th.App.UpdateConfig(func(cfg *model.Config) { *cfg.PluginSettings.Enable = true })
+
 	t.Run("SendDailyDiagnostics", func(t *testing.T) {
 		th.App.sendDailyDiagnostics(true)