Ghost: i18n error: path "errors.models.posts.postNotFound" was not found

I’m getting the following error when adding and deleting content

Technical details:

• Ghost Version: 1.21.6
• Node Version: 6.9
• Browser/OS: Chrome
• Database: SQLite

{
   "name":"Log",
   "hostname":"Site",
   "pid":25551,
   "level":50,
   "err":{
      "id":"b76e1d90-2c6b-11e8-8595-99a5c9cf6e1c",
      "domain":"https://mertcangokgoz.com/",
      "code":null,
      "name":"IncorrectUsageError",
      "statusCode":400,
      "level":"critical",
      "message":"i18n error: path \"errors.models.posts.postNotFound\" was not found",
      "stack":"IncorrectUsageError: i18n error: path \"errors.models.posts.postNotFound\" was not found\n    at new IncorrectUsageError (/var/www/ghost/versions/1.21.6/node_modules/ghost-ignition/lib/errors/index.js:79:23)\n    at Object.findString (/var/www/ghost/versions/1.21.6/core/server/lib/common/i18n.js:152:31)\n    at Object.t (/var/www/ghost/versions/1.21.6/core/server/lib/common/i18n.js:66:23)\n    at Child.then (/var/www/ghost/versions/1.21.6/core/server/models/post.js:690:50)\n    at Child.tryCatcher (/var/www/ghost/versions/1.21.6/node_modules/bluebird/js/release/util.js:16:23)\n    at Promise._settlePromiseFromHandler (/var/www/ghost/versions/1.21.6/node_modules/bluebird/js/release/promise.js:512:31)\n    at Promise._settlePromise (/var/www/ghost/versions/1.21.6/node_modules/bluebird/js/release/promise.js:569:18)\n    at Promise._settlePromise0 (/var/www/ghost/versions/1.21.6/node_modules/bluebird/js/release/promise.js:614:10)\n    at Promise._settlePromises (/var/www/ghost/versions/1.21.6/node_modules/bluebird/js/release/promise.js:693:18)\n    at Async._drainQueue (/var/www/ghost/versions/1.21.6/node_modules/bluebird/js/release/async.js:133:16)\n    at Async._drainQueues (/var/www/ghost/versions/1.21.6/node_modules/bluebird/js/release/async.js:143:10)\n    at Immediate.Async.drainQueues (/var/www/ghost/versions/1.21.6/node_modules/bluebird/js/release/async.js:17:14)\n    at runCallback (timers.js:794:20)\n    at tryOnImmediate (timers.js:752:5)\n    at processImmediate [as _immediateCallback] (timers.js:729:5)"
   },
   "msg":"i18n error: path \"errors.models.posts.postNotFound\" was not found",
   "time":"2018-03-20T18:22:58.547Z",
   "v":0
}