fix: nil deriference

[gassara-kys]

通知先が登録されてないとNil参照エラーで落ちてしまうので修正します

[github-actions]

PR Analysis

Main theme

Bug fix

PR summary

This PR addresses an issue where an error is returned when no notifications are found, providing a more specific error message.

Type of PR

Bug fix

PR Feedback:

General suggestions

Consider adding a check for nil notifications along with an empty notifications slice to handle both cases separately for clarity and to differentiate between missing notifications and an empty list.

Code feedback

relevant file:

pkg/server/alert/alert_notification.go

suggestion:

Consider adding a check to handle nil notifications and an empty slice separately for clear distinction.

relevant line:

+	if notifications == nil || len(*notifications) == 0 {

Security concerns:

no

[github-actions]

セキュリティレビューを実施しました。
特に問題は見つかりませんでした👏

By RISKEN review

[iiiidaaa]

LGTM