fix URL not found

[tatref]

If URL is invalid or if authentication is not working, the script outputs

Use of uninitialized value $haproxy in split at ./check_haproxy_stats.pl line 231.
Unable to retrieve haproxy stats at ./check_haproxy_stats.pl line 233.

Now with the fix:

Unable to retrieve haproxy stats at ./check_haproxy_stats.pl line 227.

As I'm not very familiar with Perl, there could be better ways to fix this?

Description

Related Issue

Motivation and Context

How Has This Been Tested?

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have added tests to cover my changes.
• All new and existing tests passed.