Commenting a wrong estimate time

Summary

When you try to add an estimate to an issue, using the /issue command, and fill in a wrong time format, you don't get any errors. The comment box will get cleared but nothing happens.

Steps to reproduce

1. Create a new issue
2. Go to the comment section
3. Fill in the command: /estimate 1,5h for example

What is the current bug behavior?

Field goes blank, nothing shows up or happens.

What is the expected correct behavior?

Error showing, telling you the filled in format is incorrect.