message: fix(c-api) Allow `finalizer` to be `NULL`.
diff: @@ -7,6 +7,7 @@ use std::ffi::c_void;
  use std::sync::Arc;
  use wasmer::{Function, Instance, RuntimeError, Val};
  +#[derive(Debug)]
  #[allow(non_camel_case_types)]
  pub struct wasm_func_t {
  pub(crate) inner: Function,
  @@ -91,12 +92,11 @@ pub unsafe extern "C" fn wasm_func_new_with_env(
  function_type: Option<&wasm_functype_t>,
  callback: Option<wasm_func_callback_with_env_t>,
  env: *mut c_void,
  - finalizer: Option<wasm_env_finalizer_t>,
  + finalizer: wasm_env_finalizer_t,
  ) -> Option<Box<wasm_func_t>> {
  let store = store?;
  let function_type = function_type?;
  let callback = callback?;
  - let finalizer = finalizer?;
  let func_sig = &function_type.inner().function_type;
  let num_rets = func_sig.results().len();
  