Fix dark mode in development mode

Author: shana

src/UnityExtension/Assets/Editor/GitHub.Unity/Misc/Utility.cs

@@ -37,16 +37,14 @@ public static Texture2D GetIcon(string filename, string filename2x = "", bool in
             Texture2D texture2D = null;
 
             var stream = Assembly.GetExecutingAssembly().GetManifestResourceStream("GitHub.Unity.IconsAndLogos." + filename);
-            if (stream != null)
+            if (stream == null)
             {
-                texture2D = stream.ToTexture2D();
-            }
-            else
-            {
-                var iconPath = "Assets/Editor/GitHub.Unity/IconsAndLogos/" + filename;
-                texture2D = AssetDatabase.LoadAssetAtPath<Texture2D>(iconPath);
+                stream = new MemoryStream(Application.dataPath.ToNPath().Combine("Editor/GitHub.Unity/IconsAndLogos/", filename).ReadAllBytes());
             }
 
+            texture2D = stream.ToTexture2D();
+            stream.Dispose();
+
             if (texture2D != null)
             {
                 texture2D.hideFlags = HideFlags.HideAndDontSave;