Extra lines when creating parts

When creating parts, sometimes the lines from other parts are created too in parts that do not have them.

There is no clear way to reproduce this, but the problem is present in the attached testcase.

Here is how I reproduced this in the first place (but seems to happen only sometimes, or perhaps in another conditions):

1. Create a multi-part score (e.g. 2 instruments).
2. Add a simple line (7th palette, last item) below some note and extend it, so it spans to a second row.
3. Define the parts containing 1 instrument per part.
4. Create a part that doesn't contain the above mentioned line

Result: A line was created for the wrong part.

To see this in the attached testcase do this: file->parts->Create a part for the bass.
As you can see there is a "cresc." line that shouldn't appear (should be in the flute part only).