Problem: The file "field/BlineTracer/src/G4BlineTracer.cc" is missing an include directive for "G4MagIntegratorDriver.hh" This is required to instantiate/use objects of type `G4MagInt_Driver` which happens within the file in several places Solution: Add #include "G4MagIntegratorDriver.hh" within the includes region of the file.
Thanks for reposting this. The problem is already fixed in release 10.5.