Missing file breaks aliDoctor

[ktf]

Looks like not having a build_requires recipe breaks aliDoctor.

alibuild/aliDoctor -c shipdist/ --defaults fairship FairShip
Traceback (most recent call last):
    doMain(args, parser)
  File "/media/disk0/slc8/SHiPBuild/alibuild/aliBuild", line 65, in doMain
    doDoctor(args, parser)
  File "/media/disk0/slc8/SHiPBuild/alibuild/alibuild_helpers/doctor.py", line 188, in doDoctor
    log                     = info)
  File "/media/disk0/slc8/SHiPBuild/alibuild/alibuild_helpers/utilities.py", line 318, in getPackageList
    dieOnError(spec["package"].lower() != lowerPkg,
TypeError: 'NoneType' object is not subscriptable
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