Memory leak in bin_mdef_read_text

[guidovranken]

Passing a file with the following contents to bin_mdef_read_text causes a memory leak.

0.3
10 n_base
10 n_tri
100 n_state_map
40 n_tied_ci_state
100 n_tied_state
10 n_tied_tmat
x - - - n/a 0 5 5 5 5 N
mu - - - n/a 0 5 5 5 5 N
iaaaasaa - - - n/a 0 5 5 5 5 N
aaayvfhi - - - n/a 0 5 5 5 5 N
caaaaaah - - - n/a 0 5 5 5 5 N
cagapaaa - - - n/a 0 5 5 5 5 N
dahjaaaa - - - n/a 0 5 5 5 5 N
av - - - n/a 0 5 5 5 5 N
iaaaaiaa - - - n/a 0 5 5 5 5 N
aaayvvhi - - - n/a 0 5 5 5 5 N
iaaaasaa iaaaasaa aaayvvhi b n/a 0 5 5 5 5 N
iaaaaiaa x aaayvvhi b n/a 0 5 5 5 5 N
iaaaasaa iaaaasaa iaaaasaa b n/a 0 5 5 5 5 N
caaaaaah cagapaaa cagapaaa i n/a 0 5 5 5 5 N
iaaaasaa iaaaasaa iaaaaiaa b n/a 0 5 5 5 5 N
iaaaasaa caaaaaah x e n/a 0 5 5 5 5 N
iaaaaiaa iaaaaiaa cagapaaa b n/a 0 5 5 5 5 N
dahjaaaa iaaaasaa iaaaaiaa i n/a 0 5 5 5 5 N
cagapaaa av x b n/a 0 5 5 5 5 N
iaaaasaa dahjaaaa iaaaaiaa b n/a 0 5 5 5 5 N

(Generated with a fuzzer, hence the strange contents)