Various build and test fixes

Gems/Multiplayer/Code/Include/Multiplayer/IMultiplayer.h

@@ -139,27 +139,31 @@ namespace Multiplayer
 
     inline INetworkTime* GetNetworkTime()
     {
-        return GetMultiplayer()->GetNetworkTime();
+        return AZ::Interface<INetworkTime>::Get();
     }
 
     inline INetworkEntityManager* GetNetworkEntityManager()
     {
-        return GetMultiplayer()->GetNetworkEntityManager();
+        IMultiplayer* multiplayer = GetMultiplayer();
+        return (multiplayer != nullptr) ? multiplayer->GetNetworkEntityManager() : nullptr;
     }
 
     inline NetworkEntityTracker* GetNetworkEntityTracker()
     {
-        return GetNetworkEntityManager()->GetNetworkEntityTracker();
+        INetworkEntityManager* networkEntityManager = GetNetworkEntityManager();
+        return (networkEntityManager != nullptr) ? networkEntityManager->GetNetworkEntityTracker() : nullptr;
     }
 
     inline NetworkEntityAuthorityTracker* GetNetworkEntityAuthorityTracker()
     {
-        return GetNetworkEntityManager()->GetNetworkEntityAuthorityTracker();
+        INetworkEntityManager* networkEntityManager = GetNetworkEntityManager();
+        return (networkEntityManager != nullptr) ? networkEntityManager->GetNetworkEntityAuthorityTracker() : nullptr;
     }
 
     inline MultiplayerComponentRegistry* GetMultiplayerComponentRegistry()
     {
-        return GetNetworkEntityManager()->GetMultiplayerComponentRegistry();
+        INetworkEntityManager* networkEntityManager = GetNetworkEntityManager();
+        return (networkEntityManager != nullptr) ? networkEntityManager->GetMultiplayerComponentRegistry() : nullptr;
     }
 
     //! @class ScopedAlterTime

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.
         //! @{

Gems/Multiplayer/Code/Tests/RewindableObjectTests.cpp

@@ -38,7 +38,7 @@ namespace UnitTest
         {
             test = i;
             EXPECT_EQ(i, test);
-            AZ::Interface<Multiplayer::INetworkTime>::Get()->IncrementHostFrameId();
+            Multiplayer::GetNetworkTime()->IncrementHostFrameId();
         }
 
         for (uint32_t i = 0; i < 16; ++i)
@@ -51,7 +51,7 @@ namespace UnitTest
         {
             test = i;
             EXPECT_EQ(i, test);
-            AZ::Interface<Multiplayer::INetworkTime>::Get()->IncrementHostFrameId();
+            Multiplayer::GetNetworkTime()->IncrementHostFrameId();
         }
 
         for (uint32_t i = 16; i < 48; ++i)
@@ -69,7 +69,7 @@ namespace UnitTest
         {
             test = i;
             EXPECT_EQ(i, test);
-            AZ::Interface<Multiplayer::INetworkTime>::Get()->IncrementHostFrameId();
+            Multiplayer::GetNetworkTime()->IncrementHostFrameId();
         }
 
         {