Don’t leak with /(?{})$invalid_code_block/

Don’t leak with /(?{})$invalid_code_block/

This script was leaking:

$ ./perl -Ilib -wMre=eval -e '$x = "(?{+})"; while(1){eval {/(?{})$x/}}'

The mallocked array that is allocated before compilation to hold the
code blocks was not being freed before the syntax error from the inner
pattern ($x) was propagated.