Fix empty hash instruction

When we have an empty hash the iseq should have a `newhash` but instead
had a `duphash`. To fix, check if the node's elements are equal to `0`.
If so we want a `newhash`, otherwise use the original `duphash`
instructions.

Before:

```
== disasm: #<ISeq:<main>@test2.rb:1 (1,0)-(1,2)>
0000 duphash                                {}                        (   1)[Li]
0002 leave
```

After:

```
== disasm: #<ISeq:<main>@test2.rb:1 (1,0)-(1,2)>
0000 newhash                                0                         (   1)[Li]
0002 leave
```

Fixes the test `TestYJIT#test_compile_newhash`. Related to ruby/prism#2935

0 files changed, 0 insertions, 0 deletions