Ignore unknown children in IndexedFaceSet nodes instead of throwing
Ignore unknown children in IndexedFaceSet nodes instead of throwing

This fixes loading of Carson's magnetic reconnection x3d file

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