fix crash on invalid delegate AST node #451

Job	Run time
static analysis (Elixir 1.15.x \| Erlang/OTP 26.x)	2m 20s
mix test (Elixir 1.12.x \| Erlang/OTP 22.x)	41s
mix test windows (Elixir 1.13.x \| Erlang/OTP 22.x)	1m 22s
mix test (Elixir 1.12.x \| Erlang/OTP 23.x)	49s
mix test windows (Elixir 1.13.x \| Erlang/OTP 23.x)	1m 29s
mix test (Elixir 1.12.x \| Erlang/OTP 24.x)	42s
mix test windows (Elixir 1.13.x \| Erlang/OTP 24.x)	1m 24s
mix test (Elixir 1.13.x \| Erlang/OTP 22.x)	41s
mix test (Elixir 1.13.x \| Erlang/OTP 23.x)	46s
mix test windows (Elixir 1.13.x \| Erlang/OTP 25.x)	1m 23s
mix test windows (Elixir 1.14.x \| Erlang/OTP 23.x)	1m 29s
mix test (Elixir 1.13.x \| Erlang/OTP 24.x)	43s
mix test (Elixir 1.13.x \| Erlang/OTP 25.x)	41s
mix test windows (Elixir 1.14.x \| Erlang/OTP 24.x)	1m 30s
mix test (Elixir 1.14.x \| Erlang/OTP 23.x)	46s
mix test windows (Elixir 1.14.x \| Erlang/OTP 25.x)	1m 25s
mix test (Elixir 1.14.x \| Erlang/OTP 24.x)	41s
mix test windows (Elixir 1.14.x \| Erlang/OTP 26.x)	1m 35s
mix test (Elixir 1.14.x \| Erlang/OTP 25.x)	43s
mix test windows (Elixir 1.15.x \| Erlang/OTP 24.x)	1m 25s
mix test (Elixir 1.14.x \| Erlang/OTP 26.x)	38s
mix test windows (Elixir 1.15.x \| Erlang/OTP 25.x)	1m 29s
mix test (Elixir 1.15.x \| Erlang/OTP 24.x)	44s
mix test windows (Elixir 1.15.x \| Erlang/OTP 26.x)	1m 23s
mix test (Elixir 1.15.x \| Erlang/OTP 25.x)	42s
mix test (Elixir 1.15.x \| Erlang/OTP 26.x)	38s
	28m 9s

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