HPCC-10686 - Need to check subfile after lock retry

Need to check if subfile provided in RemoveSubFile when
rechcking if sub is member of super after dirty lock.
subfile is empty in case of ClearSuperFile(calling RemoveSubFile)

Signed-off-by: Jake Smith <jake.smith@lexisnexis.com>

dali/base/dadfs.cpp

@@ -4473,8 +4473,11 @@ class CDistributedSuperFile: public CDistributedFileBase<IDistributedSuperFile>
                     {
                         sf->loadSubFiles(transaction, SDS_TRANSACTION_RETRY);
                         // potentially subfile _was_ a subfile, but isn't anymore, after dirty update
-                        if (!transaction->isSubFile(parent, subfile, true))
-                            WARNLOG("addSubFile: File %s is not a subfile of %s", subfile.get(), parent->queryLogicalName());
+                        if (!subfile.isEmpty())
+                        {
+                            if (!transaction->isSubFile(parent, subfile, true))
+                                WARNLOG("addSubFile: File %s is not a subfile of %s", subfile.get(), parent->queryLogicalName());
+                        }
                     }
                 }
                 if (sub)