Merge pull request #19092 from jakesmith/HPCC-32630-splitter-lookahead

HPCC-32630 Allow lookahead below blocking splitter

thorlcr/activities/nsplitter/thnsplitterslave.cpp

@@ -218,7 +218,7 @@ class NSplitterSlaveActivity : public CSlaveActivity, implements ISharedSmartBuf
 
                 PARENT::start();
                 initMetaInfo(cachedMetaInfo);
-                cachedMetaInfo.suppressLookAhead = true;
+                cachedMetaInfo.suppressLookAhead = spill; // only suppress downstream lookaheads if this is a spilling splitter
 
                 calcMetaInfoSize(cachedMetaInfo, queryInput(0));