Improve Error Call Signature

[DynamicCake]

No description provided.

[DynamicCake]

I made this PR to make the usage of error_call in functions not super annoying.

For example

 pub fn error_example() {
  glua.function(fn(params) {
    use num <- glua.then(case params {
      [] -> glua.error("Expected one number")
      [num, ..] -> glua.dereference(num, decode.int) // here
    })
    // ...
    todo
  })
}

leads to a

Type mismatch
   
   This case clause was found to return a different type than the previous
   one, but all case clauses must return the same type.
   
   Expected type:
   
       glua.Action(List(glua.Value), glua.Never)
   
   Found type:
   
       glua.Action(Int, a)

Also, the List(glua.Value) in glua.Action(List(glua.Value), glua.Never) never gets reached