bug(definition): exception when gathering variables

[mhanberg]

Problem

Last message received: handle_request %{"id" => 4, "jsonrpc" => "2.0", "method" => "textDocument/definition", "params" => %{"position" => %{"character" => 28, "line" => 387}, "textDocument" => %{"uri" => "file:///Users/mitchell/src/elixir/lib/ex_unit/lib/ex_unit/case.ex"}}}

** (ArgumentError) errors were found at the given arguments:

  * 1st argument: not a nonempty list

    :erlang.tl([])
    (elixir 1.17.0-dev) lib/map.ex:916: Map.update!/3
    (next_ls 0.22.2) lib/next_ls/helpers/ast_helpers/variables.ex:173: NextLS.ASTHelpers.Variables.postwalk/2
    (stdlib 5.2) lists.erl:1706: :lists.mapfoldl_1/3
    (elixir 1.17.0-dev) lib/macro.ex:626: Macro.do_traverse/4
    (stdlib 5.2) lists.erl:1706: :lists.mapfoldl_1/3
    (stdlib 5.2) lists.erl:1707: :lists.mapfoldl_1/3
    (elixir 1.17.0-dev) lib/macro.ex:606: Macro.do_traverse/4