Boards stay empty if filter it on a milestone that contains "+"

Step to reproduce:

1. Create a milestone with a "+" in its name.
2. Associate few issue to this milestone.
3. Create a new board and add a milestone filter.
4. Select the freshed created milestone.
5. Board stays empty.

To make it working:

1. Rename the milestone and remove the sign "+"
2. Display the board again.
3. Board displays the issues.