Filter out possible empty lines from fen file.

Fixes problem on Windows where fen-file contains Windows style new lines.

Reported by mbootsector
Default score to zero.

Problem reported by mbootsector

If $score is not defined it can lead to never-ending games because when flag_mate and flag_stalemate are not set,
 and when there is no score, the draw_counter is not increased. The engine will repeatedly send scoreless lines like

info nodes 0 time 18
bestmove h2h3 ponder (none)

This will continue a thousand moves or so, until some buffer overflows.