compiler errors with clang9

Summary

Compiler error with clang.

Steps to reproduce

-- The C++ compiler identification is: Clang
-- The C++ compiler version is: 9.0.1
-- The MPI C++ compiler is: /opt/local/bin/mpicxx-mpich-clang90

Relevant logs and/or screenshots

[ 45%] Building CXX object src/CMakeFiles/libOPAL.dir/Classic/BeamlineCore/RBendRep.cpp.o
/Users/jsnuverink/Documents/OPAL/fork/src/src/Classic/BeamlineCore/RBendRep.cpp:35:17: error: unused variable
      'entries' [-Werror,-Wunused-const-variable]
    const Entry entries[] = {
                ^
1 error generated.
make[2]: *** [src/CMakeFiles/libOPAL.dir/Classic/BeamlineCore/RBendRep.cpp.o] Error 1