AST generated from local declarations does not match documentation

[mpeterv]

test.lua:

local parser = require "metalua.compiler".new()
local inspect = require "inspect"
local s = "local a"
print(inspect(parser:src_to_ast(s)))

Output(omitting lineinfo, etc):

{ { { { -- `Id "a"
         "a",
        tag = "Id"
      }
    }, {},
    tag = "Local"
  }
}

Note the extra empty table. It shouldn't be there according to the docs: Local{ {ident+} {expr+}? }
Either docs should be changed to Local{ {ident+} {expr*} } or the empty table shouldn't be added when there is no rhs.