Fix null dereference (#8285)

Author: lll-phill-lll

ydb/library/yql/minikql/comp_nodes/mkql_wide_combine.cpp

@@ -456,8 +456,10 @@ class TSpillingSupportState : public TComputationValue<TSpillingSupportState> {
 
         if (bucket.BucketState == TSpilledBucket::EBucketState::InMemory) {
             std::copy_n(ViewForKeyAndState.data(), KeyWidth, static_cast<NUdf::TUnboxedValue*>(bucket.InMemoryProcessingState->Tongue));
+            
+            bool isNew = bucket.InMemoryProcessingState->TasteIt();
             Throat = bucket.InMemoryProcessingState->Throat;
-            return bucket.InMemoryProcessingState->TasteIt()? ETasteResult::Init : ETasteResult::Update;
+            return isNew ? ETasteResult::Init : ETasteResult::Update;
         }
 
         // Prepare space for raw data