Make exampleCustom.cpp work
Make exampleCustom.cpp work

Did this ever work? Without this change I get an exception [here](https://github.com/arangodb/velocypack/blob/27d5366b995ad5931418cabeb3b364ace2d8b176/src/Dumper.cpp#L543).
arangodb/Jason,arangodb/Jason,arangodb/velocypack,arangodb/velocypack,arangodb/velocypack,arangodb/Jason,arangodb/velocypack,arangodb/Jason