Interface freezes when adding two attachments

[rnbdc]

When I try to add two attachments the interface freezes. This has been confirmed both in firefox/android and chrome/android. Apparently it works well on Safari/Iphone, but we only tested in one phone.

Plugin version: 0.4.9

[rnbdc]

Roundcube 1.3.8 / Plugin 0.4.9

Attaching more than one file to a new message does not work in any android phone I've tested, both with firefox and chrome.

[rnbdc]

Can also reproduce in Desktop/Chrome or Desktop/Firefox if I force the use of the mobile interface. I have tested with jquery 3.3.1 also, just in case.