Fix an uninitialized value when building with gcc 13.2.0 (#4259)

This fix already exists on master, so this is a backport
of just this fix onto 2.11.x.  This gets rid of a possible
use of an uninitialized value warning when building with
gcc 13.2.0

Signed-off-by: Chris Lalancette <clalancette@gmail.com>

src/cpp/fastdds/core/policy/QosPoliciesSerializer.hpp

@@ -867,7 +867,7 @@ inline bool QosPoliciesSerializer<DataSharingQosPolicy>::read_content_from_cdr_m
 
     for (size_t i = 0; i < num_domains; ++i)
     {
-        uint64_t domain;
+        uint64_t domain {0};
         valid &= fastrtps::rtps::CDRMessage::readUInt64(cdr_message, &domain);
         qos_policy.add_domain_id(domain);
     }