rpl: Dont fill the index with entries that failed to be parsed

Fixes use of uninitialized memory
Fixes: msan_uninit-mem_7fd10a199a3c_6204_landing.rpl
Found-by: Mateusz "j00ru" Jurczyk and Gynvael Coldwind
Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
