TwoPoint.calculate_pk fails if first source has, and second source lacks, a PT systematic
The code in TwoPoint.calcuate_pk does not handle the two tracers it is given symmetrically; if the first is associated with a source that has a PT systematic, and the second is associated with a source that lacks a PT systematic, it will fail.
We should have a test that demonstrates this bug.
Reopening the issue to fix the problem on the two_point_refactor branch, which is our (unfortunate) branch name for the branch we are using for bug fixes to the v1.7 version of Firecrown.
Now I'm actually going to re-open the issue. If I click on the right button.
This is fixed on master PR #418, and on the branch for the v1.7.x releases (two_point_refactor, for historical reasonas) by PR #415.