[fix](cast) Fix null timezone dereference in datetime cast with timezone info

Author: suxiaogang223

be/src/vec/functions/cast/cast_to_datetimev2_impl.hpp

@@ -633,14 +633,17 @@ inline bool CastToDatetimeV2::from_string_strict_mode(const StringRef& str,
                     "invalid timezone name '{}'", std::string {start, ptr});
         }
         // convert tz
-        cctz::civil_second cs {res.year(), res.month(),  res.day(),
-                               res.hour(), res.minute(), res.second()};
-
         if constexpr (type == DataTimeCastEnumType::DATE_TIME) {
             // if not timestamptz, the given time is in local_time_zone
             SET_PARAMS_RET_FALSE_IFN(
                     local_time_zone != nullptr,
-                    "local time zone required for datetime string without timezone");
+                    "local time zone required for datetime string with timezone");
+        }
+
+        cctz::civil_second cs {res.year(), res.month(),  res.day(),
+                               res.hour(), res.minute(), res.second()};
+
+        if constexpr (type == DataTimeCastEnumType::DATE_TIME) {
             auto given = cctz::convert(cs, parsed_tz);
             auto local = cctz::convert(given, *local_time_zone);
             res.unchecked_set_time_unit<TimeUnit::YEAR>((uint32_t)local.year());
@@ -913,14 +916,17 @@ inline bool CastToDatetimeV2::from_string_non_strict_mode_impl(
         }
 
         // convert tz
-        cctz::civil_second cs {res.year(), res.month(),  res.day(),
-                               res.hour(), res.minute(), res.second()};
-
         if constexpr (type == DataTimeCastEnumType::DATE_TIME) {
             // if not timestamptz, the given time is in local_time_zone
             SET_PARAMS_RET_FALSE_IFN(
                     local_time_zone != nullptr,
-                    "local time zone required for datetime string without timezone");
+                    "local time zone required for datetime string with timezone");
+        }
+
+        cctz::civil_second cs {res.year(), res.month(),  res.day(),
+                               res.hour(), res.minute(), res.second()};
+
+        if constexpr (type == DataTimeCastEnumType::DATE_TIME) {
             auto given = cctz::convert(cs, parsed_tz);
             auto local = cctz::convert(given, *local_time_zone);
             res.unchecked_set_time_unit<TimeUnit::YEAR>((uint32_t)local.year());