Fix uninitialize members on CircleTraj

https://coverity.cern.ch/reports.htm#v13572/p10041/fileInstanceId=763988738&defectInstanceId=396412786&mergedDefectId=98206

!1089 (comment 995632)

• [2018-03-27 14:15] Validation started with lhcb-gaudi-merge#471
• [2018-03-27 17:19] Validation started with lhcb-gaudi-merge#472
• [2018-03-27 17:20] Validation started with lhcb-gaudi-merge#473
• [2018-03-28 00:12] Validation started with lhcb-clang-test#903
• [2018-03-28 00:12] Validation started with lhcb-gaudi-head-py3#106
• [2018-03-28 00:16] Validation started with lhcb-tdr-test#102
• [2018-03-28 00:18] Validation started with lhcb-head#1800
• [2018-03-28 00:21] Validation started with lhcb-gaudi-head#1814

merged

mentioned in commit 67b42dd7