For example, if I use UInt8 constant for if condition then only one branch is evaluated:
```sql
SELECT if(1, 'success', throwIf(1, 'Executing FALSE branch'))

┌─'success'─┐
│ success   │
└───────────┘

1 rows in set. Elapsed: 0.003 sec.
```

But if I use some constant expression, then both branches are evaluated:
```sql
SELECT if(empty(''), 'success', throwIf(1, 'Executing FALSE branch'))

0 rows in set. Elapsed: 0.003 sec.

Received exception from server (version 21.12.2):
Code: 395. DB::Exception: Received from localhost:9000. DB::Exception: Executing FALSE branch: While processing if(empty(''), 'success', throwIf(1, 'Executing FALSE branch')). (FUNCTION_THROW_IF_VALUE_IS_NON_ZERO)
```
{
        const ColumnWithTypeAndName & arg_cond = arguments[0];
        const ColumnWithTypeAndName & arg_then = arguments[1];
        const ColumnWithTypeAndName & arg_else = arguments[2];
        bool then_is_null = arg_then.column->onlyNull();
        bool else_is_null = arg_else.column->onlyNull();
        if (!then_is_null && !else_is_null)
            return nullptr;
        if (then_is_null && else_is_null)
            return result_type->createColumnConstWithDefaultValue(input_rows_count);
        bool then_is_short = arg_then.column->size() < arg_cond.column->size();
        bool else_is_short = arg_else.column->size() < arg_cond.column->size();
        const ColumnUInt8 * cond_col = typeid_cast<const ColumnUInt8 *>(arg_cond.column.get());
        const ColumnConst * cond_const_col = checkAndGetColumnConst<ColumnVector<UInt8>>(arg_cond.column.get());
        
        if (then_is_null)
        {
            if (cond_col)
            {
                auto arg_else_column = arg_else.column;
                auto result_column = IColumn::mutate(std::move(arg_else_column));
                if (else_is_short)
                    result_column->expand(cond_col->getData(), true);
                if (isColumnNullable(*arg_else.column))