fix(websso) remove exception when REMOTE_USER does not exist

[wtermellil]

Description

Remove exception when REMOTE_USER does not exist

Type of change

• Patch fixing an issue (non-breaking change)
• New functionality (non-breaking change)
• Breaking change (patch or feature) that might cause side effects breaking part of the Software

Target serie

• 21.04.x
• 21.10.x
• 22.04.x
• 22.10.x (master)

How this pull request can be tested ?

• Configure Web SSO without installing mod openidc, mod mellon, kerberos...
• Try to reach the login page
• Try to login through the API

Community contributors & Centreon team

• I have followed the coding style guidelines provided by Centreon
• I have commented my code, especially new classes, functions or any legacy code modified. (docblock)
• I have commented my code, especially hard-to-understand areas of the PR.
• I have rebased my development branch on the base branch (master, maintenance).

[sonarqube-decoration]

SonarQube Quality Gate

0 Bugs
0 Vulnerabilities
0 Security Hotspots
0 Code Smells

0.0% Coverage
0.0% Duplication

[kduret]

migrated to centreon/centreon#125