Merge pull request #12552 from richardkchapman/hpcc22126

HPCC-22126 Potential roxie crash in CRoxieLateStartActivity::stop

Reviewed-by: Gavin Halliday <ghalliday@hpccsystems.com>

roxie/ccd/ccdserver.cpp

@@ -1716,7 +1716,7 @@ public:
     }
     virtual void stop()
     {
-        if (!prefiltered)
+        if (!prefiltered && inputStream)
         {
             inputStream->stop();
         }