[mythtv] Compile error "invalid cast"

[Peter Bennett]

Hi David

I am getting this error compiling master on raspberry pi. Do you know 
what caused it? My response would be to change it to the simple cast 
(unsigned char*) (h), but maybe there is a better way, or maybe that 
will not work.

videoout_omx.cpp:62:77: error: invalid cast from type ‘std::nullptr_t’ 
to type ‘unsigned char*’
  #define FRAMESETHDR(f,h) ((f)->priv[3] = reinterpret_cast<unsigned 
char* >(h))
^
videoout_omx.cpp:1417:9: note: in expansion of macro ‘FRAMESETHDR’
          FRAMESETHDR(vf, nullptr);
          ^

Peter