[erlc] internal error in pass beam_kernel_to_ssa with maybe

[RobinMorisset]

On the following file:

-feature(maybe_expr, enable).
-module(maybe819).

f({X}) -> 
    maybe 
        <<_:(ok)>> ?= X
    end.

erlc crashes with the following error message:

Function: f/1
minimized/final_maybe819.erl: internal error in pass beam_kernel_to_ssa:
exception error: bad key: 8
  in function  map_get/2
     called as map_get(8,#{0 => {b_var,0},9 => {b_var,9},'@ssa_ret' => {b_var,'@ssa_ret'}})
     *** argument 1: not present in map
  in call from beam_kernel_to_ssa:ssa_arg/2 (beam_kernel_to_ssa.erl, line 1127)
  in call from beam_kernel_to_ssa:'-cg/2-lc$^0/1-0-'/2 (beam_kernel_to_ssa.erl, line 1125)
  in call from beam_kernel_to_ssa:cg/2 (beam_kernel_to_ssa.erl, line 1125)
  in call from beam_kernel_to_ssa:cg/2 (beam_kernel_to_ssa.erl, line 142)
  in call from beam_kernel_to_ssa:select_val/4 (beam_kernel_to_ssa.erl, line 495)
  in call from beam_kernel_to_ssa:'-select_cg/5-anonymous-0-'/4 (beam_kernel_to_ssa.erl, line 217)
  in call from lists:mapfoldl_1/3 (lists.erl, line 1588)

Here is another testcase with a very similar error message:

f() -> 
    {X} = fun () -> ok end,
    maybe 
        (1 = 2) ?= X
    end.