nested while and if error

```
local a,b;

while a and b do
  f()
end

while a do
  if b then
    f()
  end
end

while a do
  while b do
    f()
  end
end

decompiled output was :

local a, b = nil
repeat
until a and b
f()
end
while a and b do
f()
end
while a and b do
f()
end
end

```

Original issue reported on code.google.com by `virusc...@gmail.com` on 7 Jul 2013 at 4:36
