Fix CEX when --pseudo-init-prop is enabled

[Po-Chun-Chien]

The pseudo-init transformation introduces an 1-step delay at the beginning, so we need to remove the first element of the cex.

[Po-Chun-Chien]

Here's a simple Btor2 example from which you could observe the differences in the CEX.

When using 309e07a (latest main):

$ ./pono --witness -e ic3ia diamond_2-1.btor2 
sat
b0
#0
@0
0 00000000000000000000000000000001 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@0
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@0
@1
0 00000000000000000000000000000000 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@1
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@1
@2
0 00000000000000000000000000000000 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@2
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@2
@3
0 00000000000000000000000000000000 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@3
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@3
.
$ ./pono --witness -e ic3ia --pseudo-init-prop diamond_2-1.btor2 
sat
b0
#0
@0
0 00000000000000000000000000000000 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@0
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@0
@1
0 00000000000000000000000000000001 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@1
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@1
@2
0 00000000000000000000000000000000 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@2
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@2
@3
0 00000000000000000000000000000000 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@3
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@3
@4
0 00000000000000000000000000000000 !{$(in_main#0)<$(in___VERIFIER_nondet_uint#0)<h#<__VERIFIER_nondet_uint.return>>>}@4
1 00000000000000000000000000000000 %{$(in_main#0)<main.return>}#1@4
.

[CyanoKobalamyne]

Thanks, LGTM!