Allow stage PRESOLVING in assert_solved

This might happen if a user limit (ie time) stops the solver during presolving.

src/MOI_wrapper/results.jl

@@ -51,14 +51,14 @@ end
 function assert_stage(o::Optimizer, stages)
  stage = SCIPgetStage(o)
  if !(stage in stages)
- error("SCIP is wrong stage ($stage, need $stages), can not query results!")
+ error("SCIP is wrong stage ($stage, need $stages)!")
  end
 end
 
 "Make sure that the problem was solved (SCIP is in SOLVED stage)."
 function assert_solved(o::Optimizer)
  # SCIP's stage is SOLVING when stopped by user limit!
- assert_stage(o, (SCIP_STAGE_SOLVING, SCIP_STAGE_SOLVED))
+ assert_stage(o, (SCIP_STAGE_PRESOLVING, SCIP_STAGE_SOLVING, SCIP_STAGE_SOLVED))
 
  # Check for invalid status (when stage is SOLVING).
  status = SCIPgetStatus(o)