Fix race condition when creating directory in Repeater

[alfredbez]

PR Description

We saw a race condition in our project on production, because the directory was not on disk in line 105, but was created before line 106 was executed by another process.

You can find more information about that here:

• https://stackoverflow.com/a/57939677/2123108
• https://github.com/kalessil/phpinspectionsea/blob/master/docs/probable-bugs.md#mkdir-race-condition

Checklist

• I agree with the Code Contribution License Agreement in CONTRIBUTING.md