corrected handling of 2 error cases

[bigcat88]

1. request_integration can return error, check for that was missing.
   Fixes: Error: Call to a member function getBody() on array error on nextcloud.log
2. By adding parentheses around $result['error_description'] ?? '[no error description]', we ensure that the null coalescing operator correctly provides a fallback string when error_description is not available in the $result array.
   Fixes: Undefined array key "error_description" at /var/www/html/apps-extra/integration_jira/lib/Service/NetworkService.php#225

[bigcat88]

I tested this PR for a week, and looks like I cannot reproduce #32 , so probably this PR fixes that issue.