Escape, Un-escape issue for Notes

[UK-Universal-Support-Limited]

For "Notes", some strings are not stored correctly.
The string #\\n became the string #
The string #\n became null

Steps to reproduce

1. Open a Web browser, and login to ownCloud.

2. Input the following 3 lines in the Notes field, see the attached screen-shot Input.png
   #\\n
   #\n
   #n

3.Close the Web browser.

4.Start the Web browser, and login to ownCloud.

5.Results are the following 3 lines, see the attached screen-shot ClosedThenOpened.png
#

#n

Expected behaviour

The following 3 line should be displayed after to close the browser then to open the browser
#\\n
#\n
#n

Actual behaviour

The following 3 lines were displayed.
#

#n

Server configuration

Operating system:
CentOS Linux release 7.3.1611 (Core)

Web server:
Server version: Apache/2.4.6 (CentOS)
Server built: Apr 12 2017 21:03:28

Database:
mysql Ver 15.1 Distrib 5.5.52-MariaDB, for Linux (x86_64) using readline 5.1

PHP version:
PHP 5.4.16 (cli) (built: Nov 6 2016 00:29:02)

ownCloud version: (see ownCloud admin page)
ownCloud 9.1.5 (stable)

Contacts version: (see ownCloud apps page)
Contacts   1.5.1

Updated from an older ownCloud or fresh install:
fresh install

Signing status (ownCloud 9.0 and above):
Integrity checker has been disabled. Integrity cannot be verified.

List of activated apps:
Activity 2.3.2
Admin Config Report 0.1.1
Collaborative tags 0.3.0
Comments 0.3.0
Deleted files 0.9.0
Federation 0.1.0
First run wizard 1.1
Gallery 15.0.0
Mail Template Editor 0.1
Notifications 0.3.0
PDF Viewer 0.8.1
Provisioning API 0.5.0
Share Files 0.10.0
Text Editor 2.1
Versions 1.3.0
Video player 0.9.8
Calendar 1.4.1
Contacts 1.5.1

The content of config/config.php:

'ocx3wiccxva6', 'passwordsalt' => '***********', 'secret' => '**************************', 'trusted_domains' => array ( 0 => '*************.com', ), 'datadirectory' => '/usr/share/owncloud/data', 'overwrite.cli.url' => 'https://************.com/owncloud', 'dbtype' => 'mysql', 'version' => '9.1.5.2', 'dbname' => 'owncloud', 'dbhost' => 'localhost', 'dbtableprefix' => 'oc_', 'dbuser' => '******', 'dbpassword' => '***************', 'logtimezone' => 'UTC', 'installed' => true, ); **Are you using external storage, if yes which one:** local/smb/sftp/... No. **Are you using encryption:** yes/no No. **Are you using an external user-backend, if yes which one:** LDAP/ActiveDirectory/Webdav/... No. ### Client configuration **Browser:** Google Chrome Version 59.0.3071.115 (Official Build) (64-bit) **Operating system:** CentOS Linux release 7.3.1611 (Core) **CardDAV-clients:**