Primed the core manager cache in MRM initialization by checking if they're valid.

Author: StephenHodgson

Assets/MixedRealityToolkit/_Core/Managers/MixedRealityManager.cs

@@ -175,6 +175,11 @@ private void Initialize()
 #endif
 
                 AddManager(typeof(IMixedRealityInputSystem), Activator.CreateInstance(ActiveProfile.InputSystemType) as IMixedRealityInputSystem);
+
+                if (InputSystem == null)
+                {
+                    Debug.LogError("Failed to start the Input System!");
+                }
             }
 
             // If the Boundary system has been selected for initialization in the Active profile, enable it in the project
@@ -183,12 +188,22 @@ private void Initialize()
                 AddManager(typeof(IMixedRealityBoundarySystem), Activator.CreateInstance(ActiveProfile.BoundarySystemSystemType) as IMixedRealityBoundarySystem);
             }
 
+            if (BoundarySystem == null)
+            {
+                Debug.LogError("Failed to start the Boundary System!");
+            }
+
             // If the Teleport system has been selected for initialization in the Active profile, enable it in the project
             if (ActiveProfile.IsTeleportSystemEnabled)
             {
                 AddManager(typeof(IMixedRealityTeleportSystem), Activator.CreateInstance(ActiveProfile.TeleportSystemSystemType) as IMixedRealityTeleportSystem);
             }
 
+            if (TeleportSystem == null)
+            {
+                Debug.LogError("Failed to start the Teleport System!");
+            }
+
             if (ActiveProfile.RegisteredComponentsProfile != null)
             {
                 for (int i = 0; i < ActiveProfile.RegisteredComponentsProfile.Configurations?.Length; i++)