Vuejs 3 Bugfix for adding Eventlisteners

[danielDigitalArt]

Error-Message was:
Uncaught (in promise) TypeError: Cannot convert undefined or null to object
at Function.keys ()
at Proxy.addEventListener

Reason:
$listeners was removed in vue 3, see: https://v3-migration.vuejs.org/breaking-changes/listeners-removed.html

Hotfix:
Prevent error messages by ignoring listeners, when not set. Will surely prevent Listeners from being properly registered/executed.

Please check if the PR fulfills these requirements

• It's submitted to right branch according to our branching model
• It's right issue type on title
• When resolving a specific issue, it's referenced in the PR's title (e.g. fix #xxx[,#xxx], where "xxx" is the issue number)
• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes/features)
• Docs have been added/updated (for bug fixes/features)
• It does not introduce a breaking change or has description for the breaking change

Description

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Thank you for your contribution to TOAST UI product. 🎉 😘 ✨

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This issue has been automatically marked as inactive because there hasn’t been much going on it lately. It is going to be closed after 7 days. Thanks!

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This issue will be closed due to inactivity. Thanks for your contribution!