server: Fix a pointer to uint64_t cast in spice_replay_next_cmd()
server: Fix a pointer to uint64_t cast in spice_replay_next_cmd()

This avoids a compilation error with -Werror on 32 bit systems as the
pointer size differs from that of an uint64_t.

Signed-off-by: Francois Gouget <6b915da68578f6eb004fe99432b967565fc9be8f@codeweavers.com>

SPICE/spice,SPICE/spice,SPICE/spice,fgouget/spice,fgouget/spice,fgouget/spice,fgouget/spice