Fix search view conversation reset bug

When searching for an existing conversation using a phone number, it’s possible
to click on ‘Start conversation…’ and have that new dummy entry overwrite the
existing conversation.

This change ensures we are always showing a dummy conversation model that is not
part of the conversation collection. Adding it is always idempotent as it goes
through `getOrCreateAndWait`.

Gruntfile.js

@@ -106,6 +106,7 @@ module.exports = function(grunt) {
         '!js/logging.js',
         '!js/backup.js',
         '!js/modules/**/*.js',
+        '!js/views/conversation_search_view.js',
         '!js/views/debug_log_view.js',
         '!js/signal_protocol_store.js',
         '!js/database.js',