MessageReceiver: Add note about out-of-band updateCache calls

libtextsecure/message_receiver.js

@@ -809,6 +809,8 @@ MessageReceiver.prototype.extend({
           return null;
         }
 
+        // Note: this is an out of band update; there are cases where the item in the
+        //   cache has already been deleted by the time this runs. That's okay.
         this.updateCache(envelope, plaintext).catch(error => {
           window.log.error(
             'decrypt failed to save decrypted message contents to cache:',

ts/util/lint/exceptions.json

@@ -1244,7 +1244,7 @@
     "rule": "jQuery-wrap(",
     "path": "libtextsecure/message_receiver.js",
     "line": "          const buffer = dcodeIO.ByteBuffer.wrap(ciphertext);",
-    "lineNumber": 827,
+    "lineNumber": 829,
     "reasonCategory": "falseMatch",
     "updated": "2018-09-19T18:13:29.628Z"
   },
@@ -1252,7 +1252,7 @@
     "rule": "jQuery-wrap(",
     "path": "libtextsecure/message_receiver.js",
     "line": "        const buffer = dcodeIO.ByteBuffer.wrap(ciphertext);",
-    "lineNumber": 852,
+    "lineNumber": 854,
     "reasonCategory": "falseMatch",
     "updated": "2018-09-19T18:13:29.628Z"
   },