Merged sample fitting is broken

[kreczko]

Blame @kreczko.

The fit complains in line
https://github.com/BristolTopGroup/DailyPythonScripts/blob/master/src/cross_section_measurement/01_get_fit_results.py#L311

As it cannot find samples TTJet, SingleTop or Higgs.

[senkin]

I don't see the fix in the code — was the commit ever merged?