[CP-SAT] fix corner case in dual reduction
[CP-SAT] fix corner case in dual reduction

google/or-tools,or-tools/or-tools,or-tools/or-tools,google/or-tools,or-tools/or-tools,or-tools/or-tools,or-tools/or-tools,or-tools/or-tools,google/or-tools,google/or-tools,google/or-tools,google/or-tools