accidentally committed an = too little, which caused all unknown values to result in 'not building', which was not the intention

Dependencies

• [2] SYN2GC3O allow null values for jobs, meaning it should build
• [3] AEKIREIH * Updated hydra_eval_jobs for the new evaluator.
• [4] 4LWGZL33
• [*] 4N5APGRG * Start of a helper tool to evaluate job expressions efficiently.

Change contents

• replacement in src/c/hydra-eval-jobs.cc at line 181
  [2.7]→[2.7:38](∅→∅)
  − else if (v.type = tNull) {
  [2.7]

  [2.38]
  + else if (v.type == tNull) {