dragging kanban card doesn't write new labels

[stevegt]

This issue is:

• Bug report

Actual behaviour

1. Move kanban card between columns.
2. Leave kanban tab.
3. Go back to kanban tab, find that kanban card positions have reverted -- nothing was saved.
4. Check issue for card; labels weren't changed, so kanban card position isn't persistent.

Expected behaviour

Dragging a kanban card changes issue labels.

Steps to reproduce

See above.

Configuration

• Extension Id Used (self hosted vs simple): self hosted, v0.0.7
• tested on https://try.gitea.io/stevegt/test-kanban/issues
• Chrome version: Chromium Version 69.0.3497.81 (Official Build) Built on Ubuntu , running on Ubuntu 16.04 (64-bit)