Clean-up test files.

Also, don't add a Global Settings component at import if the xml doesn't have any global settings (option/size/custom).

PiperOrigin-RevId: 495950899
Change-Id: I6599e8ea3f3a82729fc5c974fd7ced8eb93b277e

unity/Runtime/Components/Equality/MjConnect.cs

@@ -40,6 +40,9 @@ namespace Mujoco {
       if (Body1 == null || Body2 == null) {
         throw new NullReferenceException($"Both bodies in connect {name} are required.");
       }
+      if (Anchor == null) {
+        throw new NullReferenceException($"Anchor in connect {name} is required.");
+      }
       mjcf.SetAttribute("body1", Body1.MujocoName);
       mjcf.SetAttribute("body2", Body2.MujocoName);
       mjcf.SetAttribute("anchor",

unity/Runtime/Components/MjGlobalSettings.cs

@@ -149,8 +149,7 @@ public struct MjSizeStruct {
   };
 
   public void ParseMjcf(XmlElement mjcf) {
-    var localDefault = MjSizeStruct.Default;
-    Memory = mjcf.GetAttribute("memory", localDefault.Memory);
+    Memory = mjcf.GetAttribute("memory");
   }
 
   public XmlElement ToMjcf(XmlElement mjcf) {

unity/Runtime/Importer/MjcfImporter.cs

@@ -134,10 +134,13 @@ public class MjcfImporter {
   }
 
   protected virtual void ParseRoot(GameObject rootObject, XmlElement mujocoNode) {
-
-    var globalsObject = CreateGameObjectInParent("Global Settings", rootObject);
-    var settingsComponent = globalsObject.AddComponent<MjGlobalSettings>();
-    settingsComponent.ParseGlobalMjcfSections(mujocoNode);
+    if (mujocoNode.SelectSingleNode("option") != null
+        || mujocoNode.SelectSingleNode("size") != null
+        || mujocoNode.SelectSingleNode("custom") != null) {
+      var globalsObject = CreateGameObjectInParent("Global Settings", rootObject);
+      var settingsComponent = globalsObject.AddComponent<MjGlobalSettings>();
+      settingsComponent.ParseGlobalMjcfSections(mujocoNode);
+    }
 
     // This makes references to assets.
     var worldBodyNode = mujocoNode.SelectSingleNode("worldbody") as XmlElement;