Fix a server crash

When chunk_group_row_limit is bigger than 110000, there is a crash
caused by ReadStripeNextVector().

columnar/src/backend/columnar/columnar_reader.c

@@ -2162,8 +2162,8 @@ ReadStripeNextVector(StripeReadState *stripeReadState, Datum *columnValues,
 			if (*newVectorSize == 0)
 				continue;
 		}
-
-		stripeReadState->currentRow += stripeReadState->chunkGroupReadState->rowCount;
+		else
+			stripeReadState->currentRow += stripeReadState->chunkGroupReadState->rowCount;
 
 		return true;
 	}
@@ -2260,4 +2260,4 @@ ReadChunkGroupNextVector(ChunkGroupReadState *chunkGroupReadState, Datum *column
 	}
 
 	return true;
-}
+}