Dragging an open issue to another task list sometimes marks the issue as completed

[janvlug]

Steps to reproduce

1. Drag an open task from one task list to another task list.

Expected behaviour

The issue is moved to the other task list and stays in the same state.

Actual behaviour

Quite often, the state of the task changes to completed when in the task list where it it dragged to.

Task version: 0.15.0