Avoid redundant clearing in CPU divisor sessions

PerfectNumbers.Core/Cpu/MersenneCpuDivisorScanSession.cs

@@ -35,8 +35,14 @@ internal sealed class MersenneCpuDivisorScanSession : IMersenneNumberDivisorByDi
             divisorCycle = DivisorCycleCache.Shared.GetCycleLength(divisor);
             if (divisorCycle == 0UL)
             {
-                hits.Clear();
-                return;
+                divisorCycle = MersenneDivisorCycles.CalculateCycleLength(
+                    divisor,
+                    cachedData,
+                    skipPrimeOrderHeuristic: true);
+                if (divisorCycle == 0UL)
+                {
+                    throw new InvalidOperationException($"Failed to compute a cycle for divisor {divisor}.");
+                }
             }
         }
 
@@ -45,8 +51,7 @@ internal sealed class MersenneCpuDivisorScanSession : IMersenneNumberDivisorByDi
         var exponentStepper = new ExponentRemainderStepper(cachedData);
         if (!exponentStepper.IsValidModulus)
         {
-            hits.Clear();
-            return;
+            throw new InvalidOperationException($"Invalid modulus {cachedData.Modulus} for divisor scans.");
         }
 
         var cycleStepper = new CycleRemainderStepper(divisorCycle);