Fixes in traversal in case of hash collisions.

cs/src/core/Index/FASTER/AsyncIO.cs

@@ -131,6 +131,7 @@ namespace FASTER.core
                                 Value.Free(Layout.GetValue(physicalAddress));
                             }
                             ctx.record.Return();
+                            ctx.record = ctx.objBuffer = default(SectorAlignedMemory);
                             AsyncGetFromDisk(ctx.logicalAddress, requiredBytes, AsyncGetFromDiskCallback, ctx);
                         }
                         else

cs/src/core/Index/FASTER/FASTERImpl.cs

@@ -229,6 +229,8 @@ namespace FASTER.core
                     InternalContinuePendingReadCopyToTail(ctx, request, ref pendingContext);
                 }
             }
+            else
+                return OperationStatus.NOTFOUND;
 
             return OperationStatus.SUCCESS;
         }