fix broken halfcard rendering

fix broken halfcard rendering

due to the faint hack, black cards were 1 byte shorter than red cards.
this meant, that the offset for halfcard was off for red colors (as it
has been adjusted for black cards), which caused printing errors in
spider's foundation for overlapping red cards. can't pad with zero bytes
(as that would end the string), but using an extra escape seems to be OK
for xterm and vte-based terminals.