Bug 1496220 - 1. Serialize default null principal in RemoteWebNavigation; r=jkt

RemoteWebNavigation is expected to pass a serialized principal, so the
default null principal should be serialized as well.

Differential Revision: https://phabricator.services.mozilla.com/D7784

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

toolkit/components/remotebrowserutils/RemoteWebNavigation.js

@@ -105,9 +105,8 @@ RemoteWebNavigation.prototype = {
       postData: aPostData ? Utils.serializeInputStream(aPostData) : null,
       headers: aHeaders ? Utils.serializeInputStream(aHeaders) : null,
       baseURI: aBaseURI ? aBaseURI.spec : null,
-      triggeringPrincipal: aTriggeringPrincipal
-                           ? Utils.serializePrincipal(aTriggeringPrincipal)
-                           : Services.scriptSecurityManager.createNullPrincipal({}),
+      triggeringPrincipal: Utils.serializePrincipal(
+          aTriggeringPrincipal || Services.scriptSecurityManager.createNullPrincipal({})),
       requestTime: Services.telemetry.msSystemNow(),
     });
   },