Fix error when manually adding ChasingWalkComponent to an entity (#30207)

Content.Server/Physics/Components/ChasingWalkComponent.cs

@@ -65,7 +65,7 @@ public sealed partial class ChasingWalkComponent : Component
     /// The component that the entity is chasing
     /// </summary>
     [DataField(required: true)]
-    public ComponentRegistry ChasingComponent = default!;
+    public ComponentRegistry ChasingComponent = [];
 
     /// <summary>
     /// The maximum radius in which the entity chooses the target component to follow

Content.Server/Physics/Controllers/ChasingWalkSystem.cs

@@ -61,6 +61,9 @@ public sealed class ChasingWalkSystem : VirtualController
 
     private void ChangeTarget(EntityUid uid, ChasingWalkComponent component)
     {
+        if (component.ChasingComponent.Count <= 0)
+            return;
+
         //We find our coordinates and calculate the radius of the target search.
         var xform = Transform(uid);
         var range = component.MaxChaseRadius;