[erlc] internal error in pass beam_validator_strong

[RobinMorisset]

On master:

f(X) ->
    case X of
        <<>> ->
            (true -- []);
        <<_>> ->
            X
    end /= X.

crashes erlc with the following error message:

Function: '-f1/0-fun-0-'/1
minimized/validator_get_tail_1.erl: internal error in pass beam_validator_strong:
exception error: no case clause matching {get_tail,2,1,{x,0}}
  in function  beam_validator:validate_bs_match/4 (beam_validator.erl, line 1716)
  in call from beam_validator:branch/4 (beam_validator.erl, line 2879)
  in call from beam_validator:validate_instrs/4 (beam_validator.erl, line 333)
  in call from beam_validator:validate_1/5 (beam_validator.erl, line 276)
  in call from beam_validator:validate_0/4 (beam_validator.erl, line 114)
  in call from beam_validator:validate/2 (beam_validator.erl, line 56)
  in call from compile:beam_validator_1/3 (compile.erl, line 1663)
  in call from compile:fold_comp/4 (compile.erl, line 408)

Some very similar testcases cause the same error message:

f(X) ->
    {X,
        case X of
            0 ->
                0;
            <<_>> ->
                X
        end}.

and

f1(X) ->
    f2(
        (case X of
            a ->
                X;
            <<_>> ->
                X
        end),
        X
    ).

f2(_, false) ->
    ok.