compile.c (add_adjust_info): Remove `insns_info_index > 0`

... because insns_info_index could not be zero here. Also it adds an
invariant check for that.

This change will prevent the following warning of GCC 12.1

http://rubyci.s3.amazonaws.com/arch/ruby-master/log/20220613T000004Z.log.html.gz
```
compile.c:2230:39: warning: array subscript 2147483647 is outside array bounds of ‘struct iseq_insn_info_entry[2147483647]’ [-Warray-bounds]
 2230 |         insns_info[insns_info_index-1].line_no != adjust->line_no) {
      |         ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~
```

0 files changed, 0 insertions, 0 deletions