Trying to import workboard for WMSE gives error 400. Other projects (I tried two at random) don't seem to suffer from this.

Steps to reproduce:

1. Go to WMSE
2. Click Workboard in the left hand menu.
3. Select Import Columns.
4. Click Create Workboard.

Actual result:
Page displays "400 Bad Request".

Expected result:
The next step in the import process is shown.

Additional information:
I haven't tried creating an empty workboard, which may be a simple enough workaround, in case someone wants to take a look at what's causing this.