Various build and test fixes

Gems/Multiplayer/Code/Source/NetworkEntity/EntityReplication/EntityReplicationManager.cpp

@@ -60,7 +60,11 @@ namespace Multiplayer
         // Start window update events
         m_updateWindow.Enqueue(AZ::TimeMs{ 0 }, true);
 
-        GetNetworkEntityManager()->AddEntityExitDomainHandler(m_entityExitDomainEventHandler);
+        INetworkEntityManager* networkEntityManager = GetNetworkEntityManager();
+        if (networkEntityManager != nullptr)
+        {
+            networkEntityManager->AddEntityExitDomainHandler(m_entityExitDomainEventHandler);
+        }
     }
 
     void EntityReplicationManager::SetRemoteHostId(HostId hostId)

Gems/Multiplayer/Code/Source/NetworkTime/NetworkTime.cpp

@@ -17,6 +17,16 @@
 
 namespace Multiplayer
 {
+    NetworkTime::NetworkTime()
+    {
+        AZ::Interface<INetworkTime>::Register(this);
+    }
+
+    NetworkTime::~NetworkTime()
+    {
+        AZ::Interface<INetworkTime>::Unregister(this);
+    }
+
     bool NetworkTime::IsTimeRewound() const
     {
         return m_rewindingConnectionId != AzNetworking::InvalidConnectionId;

Gems/Multiplayer/Code/Source/NetworkTime/NetworkTime.h

@@ -23,8 +23,8 @@ namespace Multiplayer
         : public INetworkTime
     {
     public:
-        NetworkTime() = default;
-        virtual ~NetworkTime() = default;
+        NetworkTime();
+        virtual ~NetworkTime();
 
         //! INetworkTime overrides.
         //! @{