Magnifier icon fix (#497)

* change magnifier icon to property and load if it's null on first get

* change local field to private

Author: brnkhy

sdkproject/Assets/Mapbox/Unity/Editor/NodeEditor/NodeBasedEditor.cs

@@ -32,7 +32,18 @@ public class NodeBasedEditor : EditorWindow
 		public static GUIStyle selectedNodeStyle;
 		public static GUIStyle inPointStyle;
 		public static GUIStyle outPointStyle;
-		public static Texture2D magnifierTexture;
+		private static Texture2D _magnifierTexture;
+		public static Texture2D magnifierTexture
+		{
+			get
+			{
+				if(_magnifierTexture == null)
+				{
+					_magnifierTexture = EditorGUIUtility.FindTexture("d_ViewToolZoom");
+				}
+				return _magnifierTexture;
+			}
+		}
 		private GUIStyle _optionLabel;
 
 		//private ConnectionPoint selectedInPoint;
@@ -57,7 +68,7 @@ private static void OpenWindow()
 		private void OnEnable()
 		{
 			GUIScaleUtility.CheckInit();
-			magnifierTexture = EditorGUIUtility.FindTexture("d_ViewToolZoom");
+			//MagnifierTexture = EditorGUIUtility.FindTexture("d_ViewToolZoom");
 			var textOffset = new RectOffset(12, 0, 10, 0);
 
 			nodeStyle = new GUIStyle();