Merge pull request #5756 from jakesmith/hpcc-11288

HPCC-11288 - regression if inside transaction

Reviewed-By: Atilla Vamos <attila.vamos@lexisnexis.com>
Reviewed-By: Richard Chapman <rchapman@hpccsystems.com>

plugins/fileservices/fileservices.cpp

@@ -1170,6 +1170,8 @@ public:
             transaction = _transaction;
             transaction->start();
         }
+        else
+            transaction = NULL;
     }
     ~CImplicitSuperTransaction()
     {