Default tie not applied for BackToBackExponential function when type is selected via the property browser

[rbauststfc]

When adding a peak in the Fit browser (see test 8, step 5 in the Engineering Diffraction manual testing instructions), if you add a non BackToBackExponential peak and then change it's type in the Fit Functions property browser to BackToBackExponential peak, the default ties are not applied. This is not a regression (appears in Mantid 6.7, perhaps earlier).

This was found when manual testing the Engineering Diffraction interface for version 6.10 (https://github.com/mantidproject/mantid/issues/37329#issuecomment-2115612227), however this is not specific to the engineering interface, it is the same in the normal fit browser. Richard has explained that it will be because it does not call setMatrixWorkspace on the function.