Backport #67306 to 24.3: Fix crash of uniq and uniqTheta with empty tuple argument

src/AggregateFunctions/UniqVariadicHash.h

@@ -67,6 +67,9 @@ struct UniqVariadicHash<false, true>
 {
     static inline UInt64 apply(size_t num_args, const IColumn ** columns, size_t row_num)
     {
+        if (!num_args)
+            return 0;
+
         UInt64 hash;
 
         const auto & tuple_columns = assert_cast<const ColumnTuple *>(columns[0])->getColumns();

tests/queries/0_stateless/03208_uniq_with_empty_tuple.reference

@@ -0,0 +1,2 @@
+1
+1

tests/queries/0_stateless/03208_uniq_with_empty_tuple.sql

@@ -0,0 +1,4 @@
+-- Tags: no-fasttest
+-- https://github.com/ClickHouse/ClickHouse/issues/67303
+SELECT uniqTheta(tuple());
+SELECT uniq(tuple());