fixes a compilation error on cray with icc
fixes a compilation error on cray with icc

the error reads like
"error: cannot convert 'float ' to 'const float ()[8]' for argument '4'
environment was:
icc 18.0.5, ispc 1.9.2, embree 3.2.0, ospray 1.8.4 all within craype 2.5.6

ospray/OSPRay,ospray/OSPRay,ospray/OSPRay,ospray/OSPRay,wilsonCernWq/ospray,wilsonCernWq/ospray,wilsonCernWq/ospray