EMCAL: initialise the MC kinematics reader pointer in the digitizer

DigitizerSpec::mcReader had no initialiser, and run() only creates the
reader when the pointer is null. When the memory the (large) spec is
allocated in is not zeroed, the reader is never created and
getMCEventHeader() dereferences garbage, crashing the digitizer at the
first collision accepted by the CTP minimum-bias trigger. Seen on macOS
in about one run in three; Linux likely hides it because large
allocations come from fresh zeroed pages.

Also initialise mCTPConfig, which follows the same pattern.

Author: ktf

Detectors/EMCAL/workflow/include/EMCALWorkflow/EMCALDigitizerSpec.h

@@ -89,9 +89,9 @@ class DigitizerSpec final : public o2::base::BaseDPLDigitizer, public o2::framew
   std::shared_ptr<CalibLoader> mCalibHandler; ///< Handler of calibration objects
   std::vector<Hit> mHits;                     ///< Vector with input hits
   std::vector<TChain*> mSimChains;
-  o2::ctp::CTPConfiguration* mCTPConfig; ///< CTP configuration
-  o2::detectors::DetID::mask_t mDetMask; ///< to keep track whether FT0 and FV0 are included
-  o2::steer::MCKinematicsReader* mcReader; ///< reader to access MC collision information
+  o2::ctp::CTPConfiguration* mCTPConfig = nullptr;   ///< CTP configuration
+  o2::detectors::DetID::mask_t mDetMask;             ///< to keep track whether FT0 and FV0 are included
+  o2::steer::MCKinematicsReader* mcReader = nullptr; ///< reader to access MC collision information
 
   DigitizerTRU mDigitizerTRU;             ///< Digitizer object TRU
   o2::emcal::SDigitizer mSumDigitizerTRU; ///< Summed digitizer TRU