Create blueslip error for undefined keys in Dict.

We create a blueslip error for undefined keys in Dict.  This led
to a straightforward change in the unit tests for Dict.  For the
unread test, to avoid the blueslip error, we had to be more specific
in setting up a user in one place, but this reduced our coverage,
leading to another small test being added.

(imported from commit 33e14795500d9283de2a7c03c4c58aec11cea4b8)

static/js/dict.js

@@ -53,6 +53,7 @@ Dict.from_array = function Dict_from_array(xs, opts) {
 Dict.prototype = {
     _munge: function Dict__munge(k) {
         if (k === undefined) {
+            blueslip.error("Tried to call a Dict method with an undefined key.");
             return undefined;
         }
         if (this._opts.fold_case) {

zerver/tests/frontend/node/dict.js

@@ -6,6 +6,8 @@ var _ = global._;
 var Dict = require('js/dict.js');
 var assert = require('assert');
 
+set_global('blueslip', {});
+
 (function test_basic() {
     var d = new Dict();
 
@@ -60,6 +62,10 @@ var assert = require('assert');
 }());
 
 (function test_undefined_keys() {
+    global.blueslip.error = function (msg) {
+        assert.equal(msg, "Tried to call a Dict method with an undefined key.");
+    };
+
     var d = new Dict();
 
     assert.equal(d.has(undefined), false);

zerver/tests/frontend/node/unread.js

@@ -196,7 +196,8 @@ var zero_counts = {
 
     var message = {
         id: 15,
-        type: 'private'
+        type: 'private',
+        reply_to: 'alice@zulip.com'
     };
 
     unread.process_loaded_messages([message]);
@@ -209,7 +210,10 @@ var zero_counts = {
 }());
 
 (function test_num_unread_for_person() {
-    var email = 'alice@zulip.com';
+    var email = 'unknown@zulip.com';
+    assert.equal(unread.num_unread_for_person(email), 0);
+
+    email = 'alice@zulip.com';
     assert.equal(unread.num_unread_for_person(email), 0);
 
     var message = {