Fix corruption when out of shape during ivar remove

Reproduction script:

```
o = Object.new
10.times { |i| o.instance_variable_set(:"@a#{i}", i) }

i = 0
a = Object.new
while RubyVM::Shape.shapes_available > 2
  a.instance_variable_set(:"@i#{i}", 1)
  i += 1
end

o.remove_instance_variable(:@a0)

puts o.instance_variable_get(:@a1)
```

Before this patch, it would incorrectly output `2` and now it correctly
outputs `1`.

0 files changed, 0 insertions, 0 deletions