Prevents multiple initialization of extension manager.

Assets/Cryville/Crtr/Browsing/ExtensionManager.cs

@@ -8,6 +8,7 @@ using System.Reflection;
 
 namespace Cryville.Crtr.Browsing {
 	internal static class ExtensionManager {
+		static bool _init;
 		static readonly Dictionary<string, List<ResourceConverter>> _converters
 			= new Dictionary<string, List<ResourceConverter>>();
 		public static ISet<string> GetSupportedFormats() {
@@ -25,6 +26,8 @@ namespace Cryville.Crtr.Browsing {
 			return _localRes;
 		}
 		public static void Init(string rootPath) {
+			if (_init) return;
+			_init = true;
 			LoadExtension(typeof(Extensions.Extension));
 			var asms = AppDomain.CurrentDomain.GetAssemblies().Select(a => a.GetName().Name).ToHashSet();
 			var modules = new Queue<ModuleItem>();