[MooreToCore] Unpacked array causes crash

[fabianschuiki]

The following input crashes the MooreToCore conversion. Might be fixed by #7625.

module {
  moore.module @top() {
    %mem = moore.variable : <uarray<1024 x l8>>
    %a = moore.variable : <l8>
    moore.procedure initial {
      %0 = moore.read %mem : <uarray<1024 x l8>>
      %1 = moore.extract %0 from 123 : uarray<1024 x l8> -> l8
      moore.blocking_assign %a, %1 : l8
      moore.return
    }
    moore.output
  }
}