Revert "Changed the order of checks since the platform can filter classes that might be null"

This reverts commit 8fe7aaa.

Author: Alexander Seeck

Assets/MixedRealityToolkit/Services/MixedRealityToolkit.cs

@@ -618,15 +618,6 @@ public bool RegisterService<T>(Type interfaceType, SupportedPlatforms supportedP
                 return false;
             }
 
-#if !UNITY_EDITOR
-            if (!Application.platform.IsPlatformSupported(supportedPlatforms))
-#else
-            if (!UnityEditor.EditorUserBuildSettings.activeBuildTarget.IsPlatformSupported(supportedPlatforms))
-#endif
-            {
-                return false;
-            }
-
             if (interfaceType == null)
             {
                 Debug.LogError("Unable to register a service with a null concrete type.");
@@ -639,6 +630,15 @@ public bool RegisterService<T>(Type interfaceType, SupportedPlatforms supportedP
                 return false;
             }
 
+#if !UNITY_EDITOR
+            if (!Application.platform.IsPlatformSupported(supportedPlatforms))
+#else
+            if (!UnityEditor.EditorUserBuildSettings.activeBuildTarget.IsPlatformSupported(supportedPlatforms))
+#endif
+            {
+                return false;
+            }
+
             T serviceInstance;
 
             try