Otherwise the movie position is zero which leads the comparison with the
stored opcode position to always be false.
Fixes#10426, a regression from cf1171d4d9.
When videos are skipped, they would sometimes not quite be seeked to the
last frame. In that case, when they are played again without being
restarted, they would end immediatly.
Now videos are automatically rewinded when they end or are skipped so
that they always start from the beginning when played again.
Fixes#10389.
Bastien Bouclet