Added null check for keyList retrieved from pEpKeyList property.

addon/content/pepmsghdrview.js

@@ -441,7 +441,7 @@ var pEpHdrView = {
     let keyList = message.opt_fields.find((e) => e.key == "X-KeyList");
     if (keyList) msgHdr.setStringProperty("pEpKeyList", keyList.value);
     msgHdr.setStringProperty("pEpPrivacyRating", rating.toString(10));
-    this.updatePrivacy(this.win, msgHdr, rating, keyList.value);
+    this.updatePrivacy(this.win, msgHdr, rating, keyList && keyList.value);
   },
 
   updatePrivacy(win, msgHdr, rating, keyList = null) {