Bug 1470030 - follow-up fixing covertiy null-deref issue, r=keeler

Summary: Coverity found this issue. We shouldn't continue if n is null because CERT_LIST_NEXT dereferences n.

Differential Revision: https://phabricator.services.mozilla.com/D1876

--HG--
extra : rebase_source : 8023a38425194099f334c6624ce2bd5f2e50cb95
extra : amend_source : 27947d33f9dbb0afa9ae5927dde874957eb4017c

security/manager/ssl/nsNSSComponent.cpp

@@ -861,9 +861,14 @@ nsNSSComponent::TrustLoaded3rdPartyRoots()
   if (mEnterpriseRoots) {
     for (CERTCertListNode* n = CERT_LIST_HEAD(mEnterpriseRoots.get());
          !CERT_LIST_END(n, mEnterpriseRoots.get()); n = CERT_LIST_NEXT(n)) {
-      if (!n || !n->cert) {
+      if (!n) {
         MOZ_LOG(gPIPNSSLog, LogLevel::Debug,
-                ("library failure: CERTCertListNode null or lacks cert"));
+                ("library failure: CERTCertListNode null"));
+        break;
+      }
+      if (!n->cert) {
+        MOZ_LOG(gPIPNSSLog, LogLevel::Debug,
+                ("library failure: CERTCertListNode lacks cert"));
         continue;
       }
       UniqueCERTCertificate cert(CERT_DupCertificate(n->cert));