Fix hasForceSpecificEquation

[fjclark]

This now returns true if there is a default equation for the force.

If this is to fix a bug...

This pull request fixes issue #279 (I have confirmed that the script supplied there now shows equal energies at lambda = 0 and lambda = 1).

• I confirm that I have merged the latest version of devel into this branch before issuing this pull request (e.g. by running git pull origin devel): y
• I confirm that I have added a changelog entry to the changelog (we will add a link to this PR as part of the review): y
• I confirm that I have permission to release this code under the GPL3 license: y

Suggested reviewers:

@chryswoods, @lohedges

Thanks!

[lohedges]

Thanks, @fjclark. Could you add an entry to the bottom of the CHANGELOG section for the 2023.4.0 release.

[lohedges]

Thanks. It looks like your branch must be behind devel (I guess you branched prior to my merge earlier), hence the conflict with the CHANGELOG file.

[fjclark]

Ah, sorry. I've updated now.

[lohedges]

Thanks, @fjclark. Good catch.