Bug 1620239 - ensure not to access null pointer; r=Ehsan

Differential Revision: https://phabricator.services.mozilla.com/D65576

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

browser/components/search/SearchTelemetry.jsm

@@ -643,6 +643,7 @@ class ContentHandler {
     let getTopURL = channel => {
       // top-level document
       if (
+        channel.loadInfo &&
         channel.loadInfo.externalContentPolicyType ==
           Ci.nsIContentPolicy.TYPE_DOCUMENT
       ) {
@@ -665,6 +666,7 @@ class ContentHandler {
 
       // top-level resource
       if (
+        channel.loadInfo &&
         channel.loadInfo.loadingPrincipal &&
         channel.loadInfo.loadingPrincipal.URI
       ) {